In Flutter how to design container with tick mark in top right edge like in the image

Question

How to design the container as shown in the image. Here is my partially achieved code

 Widget buildCard(index, selectedIndex) => Container(
        width: 150,
        decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(12),
            border: Border.all(
                color: (selectedIndex == index)
                    ? Color.fromARGB(255, 199, 16, 16)
                    : Color(0xFFEEEEEE))),
        child: Column(
          children: [
            Positioned(
              top: -10,
              right: 0,
              child: Container(
                alignment: Alignment.topRight,
                child: Transform.rotate(
                  angle: pi / 4,
                  child: Container(
                    color: Colors.amber,
                    height: 20,
                    width: 30,
                  ),
                ),
              ),
            ),

            // The Icon
            // Positioned(
            //   top: 4,
            //   right: -18,
            //   child: Icon(Icons.done, color: Color.fromARGB(255, 212, 23, 23)),
            // ),
          ],
        ),
      ); }

Answer 1

Using Stack and Clippath

Stack(
  alignment: Alignment.topRight,
  children: <Widget>[
    Container(
      width: double.infinity,
      height: 300,
      decoration: BoxDecoration(
        color: Colors.redAccent,
        borderRadius: BorderRadius.circular(20),
        border: Border.all(color: Colors.blueAccent, width: 5)
      ),
    ),
    ClipPath(
      clipper: CustomClipPathTopContainer(),
      child: Container(
        height: 60,
        width: 60,
        decoration: BoxDecoration(
          color: Colors.blueAccent,
          borderRadius: BorderRadius.only(topRight: Radius.circular(20)),
          border: Border.all(color: Colors.blueAccent, width: 5)
        ),
      ),
    ),
    Positioned(
      top: 5,
      right: 8,
      child: Icon(Icons.done, color: Colors.white,),
    )
  ],
),


class CustomClipPathTopContainer extends CustomClipper<Path> {

  @override
  Path getClip(Size size) {
    Path path0 = Path();
    path0.moveTo(0,0);
    path0.lineTo(size.width,0);
    path0.lineTo(size.width,size.height);
    path0.lineTo(0,0);
    return path0;
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) => false;
}