It is the same technique as paper piecing. You lay your first fabric on the foundation face up in the center, the next piece face down. Stitch along one side, open up the top fabric and finger press/iron press the piece (depending on the fabrics) and keep going like this til your foundation block is covered. You could staystitch around the edge of the block after the foundation is covered, to hold it all in place, using an 1/8" seam. Then decorate with embroidery stitches.