I copied a picture of a celtic knot square I liked and made a wall hanging that needs to be on point for the look I want. When I pin it to my design wall it doesn't lay flat against the wall. It is approximately 27" square.

What can I do to correct this? I want it to hang nicely on my daughter's living room wall and not just flop around!

I don't really want to frame it (the obvious solution).

could you put a piece of stiff interfacing in it? or wait, make the hanging corners on the back and put a piece of canvas in the back to keep it stiff?

I did an octagonal wallhanging with the same problem. I added a rod pocket to the back at the largest point ( and with a square that would be fairly simple). Then get a small dowel rod to fit through it when it's hanging. It keeps the shape very nicely .

Couldn't you mount it on a piece of matboard?

Sew little round rings to the back wherever needed to keep it from flopping.

I would put the triangles on all four corners in the back. I would then cut 4, 1/4 inch dowel pieces to fit on all four sides. I've also thought that you could use the bendy part of bendable straws to connect the wood in the corners. Just an idea.

Make two sleeves and sew them to the two sides that are closest to the top. Leave a small gap (no more than 4" total) in the middle at the center - the very top.

Make a V shape using two dowels and miter join them at the top (use flat dowels it's easier). Remove the hanger part of a wooden hanger (they unscrew from the wood) and screw it to the top where the V dowels meet. At this point you can probably fashion any type of "hanger" as it will be partially visible you'll want something "pretty". Or even fasten a flat picture hanger hinge to the peak and use that.

If you want to lay REALLY flat, make two more sleeves for the bottom to sides, but don't leave a gap. Just insert dowels into the sleeves as 'weight' so it doesn't flop. Just make sure whatever kind of hanger you use will support the weight of all 4 dowels and the quilt.

Thanks for all the possible solutions!
My friend Liz suggested inserting floral wire along each edge.
May try that one first as it would be the lightest weight.