I sew up the right sides of my collar and turn it inside out, as normal. With it turned, I work the corners out first. Then, I grab the scraper and put it inside the piece BETWEEN the two seam allowances. Not above both or under both, but between the two, so when I pull the fabric against it, it creates an even edge using both pieces. You may want to use bigger seam allowances to make this much easier.
With the tool firmly in between, I hold it down while at the same time gently pulling the fabric against it. You don't have to pull tight, as that will bend and warp the edge. Dig this picture:
Just pull it until the edge is tight, and let your iron do the work! For safety sake, it's best to have something hold down the scraper, like a big clip, and pull the fabric with your hand far from your iron, so you don't scald your fingers.
After pressing it with the tool in, remove it and press both sides of the piece. When finished, you should have a very tight edge, almost seeing the stitching underneath. I tried to take a picture of this, but taking a shot of a thin edge of fabric is very difficult.
I also have a bigger scraper I use to do the longer edges.
Is it weird I get so many sewing tools from Lowe's? Next time, I'll show you how to cut your fabric out with a 7-inch angle grinder.
-Cat
This black gingham fabric comes from Michael Levine, and can be purchased online here. I used the 1/8 inch squares. It's a polyester/cotton blend, but still soft. It's also VERY thin and very light. Almost feels like I'm working with silk!