You could also use the "don't sew through the paper method." That way you can press your seams whichever direction you like. Fold the foundation on the lines and sew right next to it. Use a dab of glue to hold each piece onto the foundation paper or use freezer paper foundations and & mini iron to temporarily stick the fabric onto the foundation.
If you starch the fabric until it is as stiff as paper and keep track of your Half Rectangle Triangles (mirror images boggle my mind on some days), you can rotary cut & piece Storm at Sea.