Step 1: lure t-rex to house Step2: keep your front door open, but go inside. Make him try to follow you. Step 3: fucking stab his face from a safe distance, since the opening in the indestuctible house can never be forced wider he can never get further inside than is safe for you Step4: repeat as above over days until the t-rex has bled out. a ~25 cm knife could probably still cause injuries that sum up, even on a big ass dino.

I think the hardest part is getting into stabbing range when the angry head pokes to your door.