There’s no set rule about adding borders to quilts. Borders vary in shape and size. Some quilts have borders on all four sides. Other quilts might have a border on the top/bottom or just on two of the sides. At times, a quilter might decide the quilt can stand on its own without a border.
The quilt below sports a scalloped border with a thin turquoise fabric (inner border) positioned next pink lace trim. The yellow fabric in the border was cut to show off the thin stripe in its pattern.
The blue quilt below has different border fabrics on each of the four sides. Quilt blocks are also scattered within the borders.