您可以将Stack与Positioned搭配使用，以达成此目的：

class StackExample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(),
      body:  new Container(
        padding: const EdgeInsets.all(8.0),
          height: 500.0,
          width: 500.0,
          // alignment: FractionalOffset.center,
          child: new Stack(
            //alignment:new Alignment(x, y)
            children: <Widget>[
              new Icon(Icons.monetization_on, size: 36.0, color: const Color.fromRGBO(218, 165, 32, 1.0)),
              new Positioned(
                left: 20.0,
                child: new Icon(Icons.monetization_on, size: 36.0, color: const Color.fromRGBO(218, 165, 32, 1.0)),
              ),
              new Positioned(
                left:40.0,
                child: new Icon(Icons.monetization_on, size: 36.0, color: const Color.fromRGBO(218, 165, 32, 1.0)),
              )

            ],
          ),
        ),
      )
    ;
  }
}

这样你就可以得到一些漂亮的阴影，使图标更加突出：

class StackExample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(),
      body:  new Container(
        padding: const EdgeInsets.all(8.0),
          height: 500.0,
          width: 500.0,
          // alignment: FractionalOffset.center,
          child: new Stack(
            //alignment:new Alignment(x, y)
            children: <Widget>[
              new Container(
                decoration: new BoxDecoration(
                  borderRadius: BorderRadius.circular(25.0),
                  boxShadow: [
                    new BoxShadow(
                      blurRadius: 5.0,
                      offset: const Offset(3.0, 0.0),
                      color: Colors.grey,
                    )
                  ]
                ),
                child: new Icon(Icons.monetization_on, size: 36.0, color: const Color.fromRGBO(218, 165, 32, 1.0))),
              new Positioned(
                left: 20.0,
                child: new Container(
                  decoration: new BoxDecoration(
                  borderRadius: BorderRadius.circular(25.0),
                  boxShadow: [
                    new BoxShadow(
                      blurRadius: 5.0,
                      offset: const Offset(3.0, 0.0),
                      color: Colors.grey,
                    )
                  ]
                ),
                  child: new Icon(Icons.monetization_on, size: 36.0, color: const Color.fromRGBO(218, 165, 32, 1.0))),
              ),
              new Positioned(
                left:40.0,
                child: new Container(
                  decoration: new BoxDecoration(
                  borderRadius: BorderRadius.circular(25.0),
                  boxShadow: [
                    new BoxShadow(
                      blurRadius: 5.0,
                      offset: const Offset(3.0, 0.0),
                      color: Colors.grey,
                    )
                  ]
                )
                  ,child: new Icon(Icons.monetization_on, size: 36.0, color: const Color.fromRGBO(218, 165, 32, 1.0))),
              )

            ],
          ),
        ),
      )
    ;
  }
}

截至2019年11月，我想添加第二个解决方案：
使用软件包：https://pub.dev/packages/assorted_layout_widgets

var widget1 = ...;
var widget2 = ...;

RowSuper(  
  children: [widget1, widget2],    
  innerDistance: -20.0,
  );

这将使行单元格重叠20个像素。
这个解决方案与Stack的不同之处在于Stack中的Positioned小部件不占用空间，所以你不能让Stack的大小等于它的内容，除非你事先知道它们的大小，但是RowSuper的大小等于它的所有子小部件的大小。
请注意，还有一个ColumnSuper。* 还请注意，我是这个包的作者。*

我想要的东西没有依赖性和没有硬编码的布局。* 你可以通过使重叠使用媒体查询来增强重叠方面的%。*

Widget overlapped() {
    final overlap = 10.0;
    final items = [
      CircleAvatar(child: Text('1'), backgroundColor: Colors.red),
      CircleAvatar(child: Text('2'), backgroundColor: Colors.green),
      CircleAvatar(child: Text('3'), backgroundColor: Colors.blue),
    ];

    List<Widget> stackLayers = List<Widget>.generate(items.length, (index) {
      return Padding(
        padding: EdgeInsets.fromLTRB(index.toDouble() * overlap, 0, 0, 0),
        child: items[index],
      );
    });

    return Stack(children: stackLayers);
  }

这是我的代码在轮廓图片重叠的相机图像在Flutter。
输出：Click here to view output image

Container(
    constraints: new BoxConstraints(
      maxHeight: 200.0,
      maxWidth: 200.0
    ),
    padding: new EdgeInsets.only(left: 16.0, bottom: 8.0, right: 16.0),
    decoration: new BoxDecoration(
      shape: BoxShape.circle,
      image: new DecorationImage(
        image: new AssetImage('assets/images/profile.png'),
        fit: BoxFit.cover,
      ),
    ),
    child: Stack(
      children: [
        new Positioned(
          right: 0.0,
          bottom: 3.0,
          child: Container(
            constraints: new BoxConstraints(
                maxHeight: 50.0,
                maxWidth: 50.0
            ),
            decoration: new BoxDecoration(
              boxShadow: [
                BoxShadow(
                  color:Color(0xFFdedede),
                  offset: Offset(2,2)
                ),
              ],
              color: Colors.white,
              shape: BoxShape.circle,
            ),
            child: GestureDetector(
              child: Padding(
                padding: const EdgeInsets.all(8.0),
                child: Icon(
                  Icons.photo_camera,
                  size: 34,
                  color: Color(0xFF00cde7),
                ),
              ),
            ),
          ),
        ),
      ],
    ),
  )

使用OverflowBox Package 元素并指定maxWidth值将实现此效果。
以下内容可用于行或列表视图

return SizedBox(
            width: 35, //--> list children will be 35 in width
            child: OverflowBox(
              maxWidth: 50, // --> allowing the child to overflow will cause overlap between elements
              child: Container(
                width: 50,
                child: Text((index + 1).toString()),
              ),
            ),
          );

你可以试试我的包（signed_spacing_flex）。它和普通的Row（或者Column和Flex）完全一样。但是它也允许你设置负间距，这会导致它的子对象重叠。你还可以设置当它们重叠时哪些子对象应该在上面。
在您的情况下，它将类似于：

SignedSpacingRow(
  spacing: -12.0,
  stackingOrder: StackingOrder.lastOnTop,
  children: <Widget>[
    Icon(
      Icons.monetization_on, size: 36.0, 
      color: const Color.fromRGBO(218, 165, 32, 1.0),
    ),
    Icon(
      Icons.monetization_on, size: 36.0,
      color: const Color.fromRGBO(218, 165, 32, 1.0),
    ),
  ],
),

如果需要，它也适用于展开的子对象。

基于@Lee Higgins的反向变体

const size = 32.0;
const overlap = size - 6.0;
final containers = [
  Container(
    decoration: BoxDecoration(
      color: Colors.grey[300],
      shape: BoxShape.circle,
    ),
    width: size,
    height: size,
  ),
  Container(
    decoration: BoxDecoration(
      color: Colors.grey[400],
      shape: BoxShape.circle,
    ),
    width: size,
    height: size,
  ),
];
List<Widget> stackLayers = List<Widget>.generate(containers.length, (index) {
  return Padding(
    padding: EdgeInsets.fromLTRB(0, 0, index * overlap, 0),
    child: containers[index],
  );
});
return Stack(alignment: AlignmentDirectional.topEnd, children: stackLayers);