1) Put the females and the male in cages next to each other where they can see and hear each other for a week or two.
2) After this time is up, put the hens in with the male (more into the territory of the few) or if they're in a divided cage then remove the divide so they have all the space between them
3) Watch carefully. There will be some chasing as the sex starved male gets in with the females, but it shouldn't be too serious. If anyone seems to be bullying, remove the bully, not the victim.
The hens may stop laying (if they've started when you introduce them) because of the change, but this should only last a couple of weeks.
a 1:3 ratio might be ok, it depends on the male, if it's a very frisky male then it might cause problems, as having too few females leads to the females going bald where the male pulls out head feathers, but with 3 hens I wouldn't think that the over-mating would be severe enough to cause any real damage, but it will depend on the male.
Hope this helps!