If you are making stars using diamonds, you will have to make Y seams. For the diamonds, start sewing in pairs from the center point to the outside, stopping 1/4" from end and back stitch.
To add the squares, start sewing from the outside, and sew to 1/4" from edge and back stitch again. Repeat for the other side of square. Now join these units in pairs again, stitching from the center and stopping 1/4" from end and back stitch. Now you can add two of the triangles. Sew these two units together, starting 3/8 - 1/2" in and back stitching to 1/4" and sew across, stopping 1/4" from edge and back stitching again. Now add the final two triangles. To get the seams to lay flat, press the seams for the diamonds in a circle, and the points out to the edges.
Good luck