I want make like a this Floating action button

but I can not make this .

I want know how to make it maybe it need shadow or offset

now my code

 floatingActionButton: _videoController?.value.isInitialized != null
          ? FloatingActionButton(
              backgroundColor: Colors.lightBlue[400],
              onPressed: () {
                setState(() {
                  _videoController!.value.isPlaying
                      ? _videoController!.pause()
                      : _videoController!.play();
                });
              },
              child: (_videoController!.value.isPlaying
                  ? Icon(
                      Icons.pause,
                      color: Colors.black,
                    )
                  : Icon(
                      Icons.play_arrow,
                      color: Colors.black,
                    )),
            )
          : Container(),
    );

Try this:

floatingActionButton: FloatingActionButton(
    backgroundColor: Colors.transparent,
    onPressed: () {},
    child: Container(
      height: 50,
      width: 50,
      decoration: BoxDecoration(
        color: Color(0xff92fcd1),
        border: Border.all(color: Colors.black),
        borderRadius: BorderRadius.circular(100),
        boxShadow: <BoxShadow>[
          BoxShadow(
              color: Colors.black,
              offset: Offset(2.5, 2.5),
              spreadRadius: 0.1)
        ],
      ),
      child: Center(
        child: Icon(
          Icons.chevron_left,
          color: Colors.black,
          size: 36,
        ),
      ),
    ),
  ),