I have done this a few times, I hope it works for you. When you are making your square leave at least one half an inch of the backing fabric extra around the whole square, to put squares together place two squares together fronts matching, move the back seam and batting away and sew a quarter inch seam down the sides you want together. Then on the back side return the backing and batting to their original places and turn under one of the back seams and sew it over the other back seam. This looks better if done by hand but I have arthritis and sew them together by machine. I am afraid this will not be clear enough, but hope it is understandable.