Wherever you feel comfortable that you can intervene if necessary. I like the bath for first intro as its easy to split scuffles. I put a bath mat in to stop bunnies slipping about and some hay for a distraction. The smaller the space the better at first.
I bonded Nushka & Bungle on Sat and went - bath, bathroom floor, run , crate and run and I'll move them to their new home once i see cuddles and grooming.