Help loom knitting blanket shawl

I want to loom knit myself a blanket shawl. I made my own version of an afghan loom using the Martha Stewart loom that you can connect yourself. I’ve tried several times using the single knit used in an afghan loom, all the edges end up curling. Any advice about how to prevent this while still doing a single knit?

I’m looking to make something that looks like this:




Are you using a weaving loom? Most of the people here knit with two needles, but some may also weave. Since it’s fewer than knitters you may need to wait for a response.