Cut a 15 by 22 1/2-inch rectangle of fabric in the color you plan to use for the base of your flag.
Fold over raw edges on one short edge and both long edges 1/2 inch. Press using low heat. Fold over 1/2 inch again. Press and pin. Stitch along the folded-over edges.
Fold the remaining short edge over 1/2 inch. Press. Fold over again 2 inches. Press, pin and stitch as for side edges. You have created a casing at the top of the flag for the flagpole to slide through.
Draw or trace the design for your flag onto scraps of fabric using a fabric marker. Cut out the design pieces 1/2 inch larger than the marked lines.
Pin the cut-out design pieces onto the flag where desired. Sew the scraps onto the main part of the flag, using a closely spaced zigzag stitch along the marked lines on the edge of each piece. Trim away excess fabric outside the zigzag lines after stitching.