Most boxing gyms don't take on staff like that to be honest, I think you would normally either go self employed and ask them if you could some cards/a poster in the changing room/what ever or seak employment somewhere like a large gym/health club were they are likely to have a permanent position.

Most clubs don't have a lot of money, they're not gonna bring in staff they don't use all the time, so it becomes more of a case of working with them, rather than for them. Finish your training then just get your name known with clubs... share kids get nothing

I'm currently pestering gyms to put my throw an apprenticeship with this training company in gateshead.