Hi!
Could you tell us a bit more about the bunnies? How long have you had them, are they both neutered, have you done any prebonding?
Assuming they’re neutered and you’ve prebonded:
The first thing I would suggest is never leaving carriers out during bonding, as it can result in a nasty fight if one feels trapped in the carrier.
If both rabbits are fixated on you rather than each other, you need to remove yourself from the bonding area but still be available to jump right in if needed. I would suggest a small, neutral area (you don’t say if your kitchen is neutral), and just leave them together for a short amount of time, another 15 minutes since the first 15 minutes sounds like it went fine. If you think one of them is starting off very scared, then you can put them both next to each other and pet them at the beginning of the session, then back off a bit and let them interact. Don’t sit in there with them, because you’re obviously distracting them. A bathtub is a good option as you can observe easily and reach in to grab them if needed, but you’re not in the space with them so they won’t keep trying to interact with you.
Postive interactions – grooming themselves or each other, flopping (together or separately), sharing food (leave this for later sessions, don’t start with it), mirroring, loafing.
Neutral – humping for less than 10 seconds, nipping, ignoring
Negative – biting, fur pulling, chasing, humping that’s distressing the other bunny, boxing, circling, face humping. All of these behaviours should be stopped immediately.
To be honest, they didn’t fight, so that’s a great start!