I have discovered Wonder tape! Love this stuff. If you are doing a pillowcase type finish and just can’t get those pesky edges to fold in and stay aligned, wonder tape is your friend! It is two sides and tacky so you can reposition the cloth to your hearts content and when you are happy you can use an iron to fuse it down to it will stick really hard. Then you can sew it. It’s a convenient 1/4 inch wide so makes getting that seam to match with the other side of the opening you want to close really easy. After you sew it, it will seems kinda stiff with that tape in there. But it sewed easy and didn’t gum up my needle. The wonder part comes after you wash the item. The tape dissolves away and disappears leaving no trace it was ever there!
I used this in my free form table runner class yesterday and the students projects came out fabulous. Even the beginner never ever sewed before student produced a really well done project. You could not tell where the opening was that was used to turn the table runner inside out.