clipped_card.dart

class ClippedCard extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return ClipPath(
      clipper: CardClipper(35.0),
      child: Container(
        alignment: Alignment.bottomCenter,
        decoration: BoxDecoration(
          color: Colors.white,
          borderRadius: BorderRadius.only(topRight: Radius.circular(60.0), topLeft: Radius.circular(60.0))
        ),
        height: 100.0,
      ),
    );
  }
}

class CardClipper extends CustomClipper<Path> {
  final double radius;

  CardClipper(this.radius);

  @override
  Path getClip(Size size) {
    var path = new Path();
    path.lineTo(0.0, size.height);
    path.lineTo(size.width, size.height);
    path.lineTo(size.width, 0.0);
    path.addOval(Rect.fromCircle(center: Offset(size.width  / 2, 0.0), radius: radius));
    return path;
  }

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

Clipped Card Example