Hi Elaine,
Yes, that's one way to do it. Alternately, you could rinse each design before joining them together. I think I personally lean toward stitching before rinsing. While you stitch the blocks together, you will need to use a zig-zag or similar wide stitch, in order to stitch two blocks together at a time. When you wash the stabilizer away, the lace sections will be held together by your zig-zag stitches.
Elaine F.
I understand about making individual lace designs on water soluble stabilizers, but when making the lace quilt, it just seems impossible to me! Sew on the stabilizer, sew the stabilizer blocks together, and wash!?