I use this way to make wreath frame for canvas on cardboard, the round shape.

You need:

-woolen fabric, flannel or felt

-cotton thick threads

-glue

When the painting is ready, glue a piece of fabric on the back side and cut off excess fabric, leave ~0.5 cm for fabric going beyond the cardboard round.

Tie a knot on the thread, fasten it to the fabric that going beyond. And sew on a wreath, catching the fabric and several branches from the wreath in turn. At the end, fasten the thread by making a few stitches in one place.