love this method, have been doing it with layering fabric layered with iron on interfacing, right sides together. I mark the circles on the interfacing side because it's easy to draw on. I hate wasting fabric so i put small circles in the spaces between the big circles. Sewing is a pc of cake when then you can just slit the interfacing, turn and iron on to hold in place while you do the blind hemstitch round the outside... then, just like yours, i slice into 4 separate 'drunkard's path' blocks and then trim away the base fabric under the circle 'section' (the iron on will come away with the base fabric) ...they can, of course, be any size.