Made a blanket and the sides curl up a bit?

This is probably a repetitive question…but I finished making a blanket in stockinette stitch and it curls up on the sides. Just a little though…because the yarn I’m using is heavy and the blanket is big. It doesn’t curl from top to bottom because I’ve added seed stitches on the top and bottom. But on left and right…I also tried to stop the curling by knitting 2 garter stitches at the beginning and end of each row while in the process of making the blanket… But I guess that didn’t help.

Would adding a border by picking up stitches at the sides help to stop the side curl?

If so, how wide should the border be to achieve this? Thanks!

Two stitches at each side surely won’t help keeping such a big thing from curling… And about the picking up stitches, I don’t know. You could have done something from 5-10, if not more, in my opinion. But that’s only me…

Stockinette curls. It’s just the nature of the beast. A border of 5 rows or so will help it stay flatter.