Terri, the muslin I used was very light weigght and loose weave so I just joined the blocks right side together, 1/4" seam in the normal way. The machine did 'grumble' a little here and there but I think this was more to do with all those seams than the extra muslin! It is a little thicker of course and I haven't batted and backed yet so i don't know how the quilting will work. I'll probably machine quilt the blocks maybe along the 'common' orange strips that give the sashing effect then hand quilt the border, which is only single fabric thickness. I'm waiting for batting to come but I'll let you know how I get on! My view was it's only scraps and a couple of days work so lets just wing it!
K x
PS My son is insisting on a piece of (thick) plaid flannel for the back - to add to the potential problems!!!