This is my method for making single fold bias tape. I used it to make the waistline detail on this dress:
Cut out strips of fabric on the bias that are about 1/2 to 1 inch wider than what you want your bias tape to be.
Sew/serge the strips of fabric together at a 45 degree angle until you get the length of fabric needed.
If you are using non-patterned fabric, it may help to draw lines down the wrong side of the fabric strip to mark where you are going to fold it.
To the ironing board now! You need an iron (obvs) and a piece of thin cardboard, or something else straight, hard and un-meltable. The cardboard helps to iron the fabric in a perfectly straight line. As long as you don’t put the iron directly on the cardboard, I wouldn’t worry about it scorching. Just stay with the iron while it is on, as usual.
Place the fabric right side down. Use the cardboard as a a guide to fold the fabric over 1/4 to 1/2 inch and iron in place. Do this all the way down one edge of the bias tape.
Then go down the opposite edge of the fabric and do the same thing, folding the fabric over and ironing it in place.
I like to turn the bias tape right side up and give it one last pressing along the entire length. That’s it!
Use in whatever projects call for single fold bias tape, or just amass a huge stash of it! (like my great grandmother did- I inherited an overflowing box of bias tape that I have managed to whittle down to one shoebox full)