Lay your strips on the ironing board.
This is the measured end while you sewed. You see it is very evenly staggered in.
What I do first is to give the whole piece a good dousing with spray starch. Spray starch is your friend! If the strips are stiff, it is much easier to cut them as they don't "squiggle" around as much.
So take the flowered, blue and tan strips in the photo and fold them down over the pink one. (Your fabrics may be different!) Your seam will face away from you.
Press the top seam the length of the piece. Don't attack it with the iron and push down the length of the seam. All that will do is stretch the seam! Be gentle!
Down with the iron, press..... up with the iron, and move down the strip further and press, up with the iron, move the iron and press... starch, starch, starch.
Very important! Be sure there aren't any little tucks or creases where the seams are pressed. You want your seams to be all the way flat without any tucks. Little tucks where the fabric isn't completely ironed over at the seam will really mess up any quilt project!
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If you have to, get your fingers under there and push the seam away from you and press.
Don't burn your fingers!
Stubborn spots can be re-sprayed with starch to make them co-operate.
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PRESS!
Remember, press all the seams in the same direction. In this case they will all be away from you.
If your run your iron widly over the fabric strips, pushing and shoving it you will stretch it onto an unreconizable mess. PRESS, up with the iron, down with the iron... PRESS!
Why? So when you sew two rows together and there is seam matching, you want your seams to be going one way on one piece and the opposite way on the strip you are sewing it to. The seam will butt together for a prefect match! Honest!
And if you happen to want to turn one upside down (yes you can do that!) you can just flip the seams up or down. It works really slick.