I've only bonded once but tried to keep it low stress because Barney has snuffles.
I started with swapping items for scent and litter trays for a few days. Then I showed Barney this new rabbit, in a fairly neuteral (not completely but not his territory and sprayed with vinegar beforehand) area - with Annabella in her temporary cage and Barney in the hallway. I didn't let Barney go right up to the cage, I just wanted to check they weren't going to go into full-attack mode at the sight of each other before starting bonding. In hindsight I probably wouldn't do it again but neither showed signs of aggression.
Then I did 'dating' for a few hours each session in a medium neutral bedroom with them free-range so they could interact or not, however they liked. I provided a litter tray, a tunnel, a water bowl and after the first one I scattered some food about too, so there were distractions. They were getting along fine but mainly ignoring each other so after just about 3 I then had them in the same situation but 24 hours a day, for 2-3 days I think, can't remember.
That was fine so I introduced Barney's cage but neutralised with vinegar and halved it so they had only roughly 8-10sqft. Probably kept them like that for 36-48 hours. Then put them in a carrier whilst I moved the cage into Barney's territory (having neutralised the area the cage went in). Then after a couple of days I enlarged the cage to its full size and started to leave them unattended. Less than a day after I did this, they escaped the cage whilst I was at work! I hadn't even neutralised the whole room yet, but they were fine so I figured bonding was done! Although I did leave them in the cage for about 16 hours a day for the first week or so, as they still seemed a bit disinterested in each other.
It was the easiest thing in the world to bond them, not one speck of aggression, but they've always been more friends than best friends and as she has gotten older Annabella has decided she wants to be more dominant, especially when Barney is ill. Once they nearly split and I had to keep them apart but able to see/smell through mesh. I had to rebond in a way, although the bond wasn't completely broken. I neutralised everything and 'dated' them for lengthening periods of time and took them on a few vet trips together (I usually take Barney alone as Anna gets stressed but he doesn't), then kept them in the (large) pen for a week. Seemed to do the trick, but I do have to watch Annabella still when Barney is ill and make sure she doesn't 'claim' areas as her own.
