As others have said, I use regular paper or newsprint (no ink) on the underside of the block when satin stitching. Someone mentioned trying to iron it flat, BUT if you want to try this, I would put a thick towel on the ironing board, then place the block face down on the towel, mist it lightly & press. The only problem you might have with this is, if you didn't prewash your fabrics they might shrink a little or pucker where the stitching is so tight. If you used Rayon thread rather than cotton, don't use a hot iron.