Circular needle

If my slouchy hat pattern says to use double pointed needles, can I use a circular needle instead and put in a marker at the starting point?

You can use a circular needle but you may come to a point where there are too few sts on the needle and you’ll need to either switch to double pointed needles or use magic loop or 2 circular needles to be able to work the small number of sts.

Yes you can. If your needle is longer than 16 or 20" you’ll need to use the magic loop or single loop technique.