I suppose it could be possible but probably highly unreccommended as one will still have hormones and will want to mate while the other won’t. Both may get aggressive with each other if not fixed, so I would fix them both before bonding.

You should have them both fixed before trying to bond. While neutering to prevent reproduction is the MAJOR reason, secondary to that is to reduce their territorial and instinctive behaviors. An unneutered male would just try to mount the female, which would most certainly lead to a fight and cause you serious problems with bonding. An unspayed female will be extremely territorial and hostile toward the male. In either case, you are up for plenty of fights and undesirable behaviors. In fact, most say that it really isn’t possible to bond if they are not both altered. Every fight they have makes their relationship worse. I would not attempt it until both are altered and given at least 1 month to recuperate.

All good info so far, short answer is both should be spayed/neutered for lots of reasons. 

Also! If you currently do not have a bunny, and there is a rescue near you, consider adopting an already bonded pair!

Rescues often have pairs looking for homes, and it saves you a TON of work and stress. The rescue in my town even basically gives you a 2 -for- 1 deal when you get a pair, and only charges you the adoption fee for one rabbit. 

It is possible (I have done it) but I would not recommend it. The only reason I did it (unspayed female, neutered male) was because the female was too old to risk spaying, but when she lost her bonded friend (another unspayed female) she was very depressed. I would definitely recommend spaying/neutering though, for the reasons suggested above. I got lucky with mine bonding so easily I think. I still have the male (Terry) and he seems to be some sort of miracle rabbit that bonds to other rabbits instantly and makes them like him.

Shelters tend to only sell spayed/neutered rabbits, so I would look there. Spaying/neutering isn’t cheap, so in my area at least, it is actually way cheaper to adopt an already fixed rabbit than to do it yourself. I feel bad for the shelters though, they lose so much money on the rabbits.