I have a 3090 strix OC and I want to put a water block in my system.
How can I make it if there is a sticker to remove the pcb plate?
You will void your warranty.
That is the reason why a lot of people go with EVGA, even thou their cards failure rate is high, but they will allow you to dismantle their card without effecting warranty.
Be warned, Asus is very picky, they will look for smallest reason to deny you claim if you need to submit RMA for any reason.