I use Leah Day's way of getting my fabric straight. If you go to Youtube she has a video on how to do it. But basically, you have to hold the selvedges together, but make sure the fold is straight. Move your fabric side-to-side until the fold is even. Then gently lay it down (at this point I press the crease very carefully) then fold in half again, doing the same thing. I always iron the crease because I find I don't get an excess of fabric at the fold. Then I arrange it on the board so that it's even along the bottom and the side, using the lines on the board. I just use 1 ruler to and make sure the fold is even across a mark on the ruler. This works for me.