在Flutter中，可以使用BottomAppBar和FloatingActionButton来实现凹槽式底部应用栏。下面是一个包含代码示例的解决方法：

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Bottom App Bar Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Bottom App Bar Demo'),
      ),
      body: Center(
        child: Text('Content'),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // Add your onPressed logic here
        },
        child: Icon(Icons.add),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
      bottomNavigationBar: BottomAppBar(
        shape: CircularNotchedRectangle(),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            IconButton(
              icon: Icon(Icons.menu),
              onPressed: () {
                // Add your onPressed logic here
              },
            ),
            IconButton(
              icon: Icon(Icons.search),
              onPressed: () {
                // Add your onPressed logic here
              },
            ),
          ],
        ),
      ),
    );
  }
}

在上面的代码中，Scaffold组件被用来创建一个页面布局，其中appBar定义了顶部的应用栏，body定义了页面的内容，floatingActionButton定义了浮动操作按钮，bottomNavigationBar定义了底部的应用栏。

BottomAppBar的shape属性被设置为CircularNotchedRectangle()，以实现凹槽效果。Row组件被用来放置底部应用栏的两个图标按钮IconButton。

通过修改onPressed回调函数，可以在按钮被点击时执行相应的逻辑。