Step 3: Hem the edge
Working on the wrong (back) side of your patterned piece mark a line 1" in from the cut edge, all the way around your big circle. Fold the raw edge in to meet this line and press with an iron set to the correct temperature for your fabric. Ease in the surplus fabric as you go and mind you fingers with the iron - turn off your steam to avoid scalded fingertips.
Now stitch the fold down, about 1/4" in from the fold.
Now mark another line 4" in from your fold and again fold your fabric in to meet this, and again press, giving a 2" hem. This time there will be more excess fabric to take care of, I pleated mine as I went around.
Fold your whole circle into eighths and press the folds firmly. Now unfold it all again.