Trios are notoriously hard, and often impossible to bond. In rare instances, it is possible for a trio to be successful and all 3 rabbits to like each other, but that seems to be the exception and not the rule.
There are also risks in even attempting to bond a single bun into a bonded pair. Trying to bond a third bun runs the risk of breaking up the current bonded pair. Or if the 3 rabbits do manage to bond to some degree, what often happens is that two rabbits pair up and consistently leave the other rabbit out. And this may not necessarily be the bonded pair you start out with. Sometimes the pair breaks up and one of the rabbits forms a bond with the single bun, while still leaving out the third bun.
The only experience I have to share is that I would usually try and bond the two more difficult rabbits first, then attempt to bond in the third if the first two do end up bonding. One trio I attempted, the two females never got over hating each other, so I was ultimately unsuccessful. I ended up keeping the rabbits as separate bonded pairs.
If you still want to risk it and attempt to bond the trio, it's important to be aware of the risks, so you better know what behavior you need to watch out for. One thing I always recommend before any bonding attempt, is lots of research on bonding, and a very thorough understanding of rabbit body language and the signs of escalating aggression in rabbits. If you know the signs of escalating aggression in rabbits, it will help to know when it's essential to intervene and stop the bonding (sometimes permanently) before any injuries can occur between the rabbits. Because rabbits intent on really hurting each other, can cause extremely serious injuries, sometimes fatal.
And don't forget having adequate protective gear (heavy duty gloves, boots, soft broom, etc) to protect yourself when intervening, so you don't end up getting latched onto with those teeth.
https://wabbitwiki.com/wiki/Bonding_rabbits_together
https://rabbitsindoors.weebly.com/bonding-bunnies.html
https://cottontails-rescue.org.uk/information-resource-centre/health-and-welfare/bonding-bunnies/
https://www.rabbitsonline.net/threads/when-to-intervene-rabbit-bonding.104770/
https://rabbitsindoors.weebly.com/uploads/2/0/6/4/20646190/the_language_of_rabbits.pdf
