For a project like that, I would get out the Elmer’s school glue. Use a small bead about 1/2” from the edge, iron with a pressing cloth, sew and remove base layer, , layer the next shape on top. Continue until all layers are secured with glue, and the back cloth has been removed. Starting with a walking foot, sew around the large piece, and move progressively to the center. (Glue will just pull loose as long as you are light handed with it. as you remove back layer from each shape)