Live USB with persistent storage for Ubuntu 20.04

I would like to run a Live USB distribution of Ubuntu 20.04 and have additional persistent storage on the USB. I tried using the instructions below, along with the ones below that to find & replace "quiet splash" with "persistent ". However, when I actually boot it, it seems to start, but also act unstable (Firefox would not load quickly and had trouble going to https://www.google.com). Additionally, I have no idea how the persistent partition is supposed to work, such as where it's mounted and what can save to it. Does anyone have any experience doing this recently, or can they point me in the right direction here? I've done searches but there's just too much old information to find anything reliable.

https://www.linuxuprising.com/2019/0...rage-live.html

https://askubuntu.com/questions/1181...h-ubuntu-19-10