The small plain squares can be made into two triangles and sewn in easily that way. The larger squares could be constructed the same way, but then you'd have to applique the small stars ontop of them. It sounds like the construction of this top was intended to be done with set-in seams, but I really think it would have been easier constructed with those stars you have completed partially assembled, with the points assembled into the rows inbetween them. Not a big help, since your stars are already complete, unless you feel like doing some unsewing.