Am I correct...The "thickness" is the width of the band, right?
If that's the case, just cut it out to whatever size you want, lay out the quilt top the floor (since it's very large) and then place the ring wherever you want it. Pin it securely and baste it in place to make sure it stays put. Then, simply stitch it in place with hand applique or machine zig zag. The key is to keep it secure so the edges dont get wonky when you're sewing it in place. I's hand baste it thoroughly. 'Hope this helps!
PS
I'm so sorry for your loss!