I cant remember if i used a pattern or not.
I probably started with a pattern and then did it my own way to get sizes i wanted.
Its been a few years since i made one but i think i just knitted a rectangular base, picked up the stitches round the outside of the rectangle and knitted in the round until it was the right length. Does that make sense? (This is for a flat bottom one)
Then just felt in the machine, i used a Drops yarn i think? It was cheap and i just ordered a load in colours i liked.
Handles i sourced from either eBay, (China mostly as cheap but take ages to come) Etsy or my friend looked out at car boots and charity shops for mega cheap bags with nice or interesting handles, and i reused those
I also did a couple that i just knitted in the round then did a 3 needle bind off and felted, they were easy to do and didnt need a pattern
I should also add i have a half finished bag in a box somewhere