I have made about 10 biscuit quilts.
The bottom square is cut at 3-1/2", top at 4-1/2". Sew 3 sides together, put a tuck on each side to make same size as bottom. stuff loosely with polyfil. If you stuff too full it will be hard to sew them together. After they are all sewn together, cut back and use the pillow case method. Bind and tie at each intersection. I have a pamphlet type book with instructions.