I waas going to mention the hammer trick, but Betty beat me to it. It really works, especially when you press the seams open and kinda make the middle a spiral. Sometimes you just have to be firm with the fabric and MAKE it do what you want. LOL
Sue

If you haven't cut all of your fabric, I would recommend heavily starching the fabric before cutting the strips. The way I do this is to mix a 1:1 solution of Sta-Flo liquid laundry starch and water, "paint" the solution on the yardage with a large wall painting brush until the fabric is saturated, toss in the dryer, then iron with steam. It comes out with about the stiffness of cardboard. This will help prevent your bias edges from stretching.

It sounds as if the "poof" you are getting in the middle of your stars may be caused by stretched fabric. In this case, spraying with spray starch and pressing up and down with an iron may help shrink the stretched areas back into position.

Also, when sewing stars, are you aware of "fanning" the center seams? This helps reduce bulk at the very center. I think the Eleanor Burns website has some diagrams that show how to do this; there must be other tutorials online too. It's a simple technique, but it helps a lot with the center bulk in stars.

I would starch heavily.
You also mention you "then sew two blocks and two blocks, then join those two sections to complete the block"

Before you join the two sections, make sure that the 2 seams you are about to sew are perfectly straight. If they are not straight at this point, your block will not be flat. You can try blocking the 2 halves to get the seams straight.

Update: I appreciate all the tips. Unfortunately, I have cut all the pieces so some tips are obsolete at this point. However, today I took a deep breath and worked on #4 block.....I carefully pinned all the pieces AFTER I mareked the end point with a 1/4" on each seem to converge at the middle point. I then carefully matched up all the side seams to make sure they all lined up. I then sewed CAREFULLY and pressed CAREFULLY. On the final seam between the two halves, I started at the center and sewed out to the end and then began again at the center and went the other direction. I pressed the final seam open and (happy dance).....it lays FLATTER; notice I said flatter as there is still some play in the fabric, but I am now convinced that this situation is one of those we have to live with! Thanks to all who offered help. This is the greatest site ever!!!

(I use a 16 oz Vaughan framers hammer to beat it into submission) :lol: Fabric is protected of course.

It doesn't take much to stretch the bias sides. I starch my fabric pretty good before cutting, and it keeps them nice and straight :D:D:D

When I'm making 8-point stars, I sew two together, press and make sure they're square. If necessary I trim with my rotary. When I sew two of these sections together I press and make sure there is a straight line. Again I will trim if needed.