I made mine at first by the pattern I found on the web but soon altered it to make it easier to make & use. Type in "free pattern, potato baker bags." Click on the tipnut.com website. When it comes up, scroll down and click on Potato Baker Bags tutorial. There you will find complete instructions on how to make the bag.
The lip is the most difficult area to work with and is not really necessary. After about a dozen bags, I just flipped the top over like a purse. Easier to make & to use! I turn the bag face down while cooking the potatoes.