Add border radius to all corners
Container(
height: 150,
width: 300,
decoration: BoxDecoration(
color: Colors.pink,
borderRadius: BorderRadius.circular(30)
),
),Output:

Add border radius specific corners
Container(
height: 150,
width: 300,
decoration: const BoxDecoration(
color: Colors.pink,
borderRadius: BorderRadius.only(
topLeft: Radius.circular(20),
topRight: Radius.circular(20),
// bottomLeft: Radius.circular(20),
// bottomRight: Radius.circular(20)
)),
),Output:
