What am I doing wrong!?

Hey theee experts. I have tried installing sequoia a few times now and every single time I run into issues: opening apps can take minutes: system freezes: returns to login screen etc etc. It’s totally unusable and I so each time I have returned to native Monterey. I’m following the steps as per the oclp instructions but I must be doing something totally dumb@ss. System is iMac 17,1. With 1tb Fusion Drive (32gb ssd). Is there a completely idiot proof set of instructions so I can see what I am doing wrong? It may be tha the system just doesn’t want to have anything newer installed (maybe a diva machine!?). Thanks in advance and appreciate any insight.