Answers for "css border only left"

container border left

Container(
  decoration: BoxDecoration(
  	border: Border(
  		left: BorderSide(color: mainColor, width: 3),
  	),
  ),
),

set border only left and right css

border-color: red green white blue;
border-style: solid dashed dotted solid;
border-width: 1px 2px 3px 4px;