Using an embroidery hoop
Start by separating the two parts of the hoop by undoing the screw. Place the inner part of the hoop on a flat surface, then place your ironed fabric over the top, before pressing the outer part of the hoop over the inner hoop, catching the fabric and keeping it as tight as possible. Do the screw back up. Flip the hoop over, and gently pull the edge of the fabric while you hold the hoop to get a taught surface for stitching.