I think that wherever you post your work/services, you might need to initially build a pretty large user base or following. That might be the first step, since an unknown or new user might just get looked over, or lost in the large amount of activity. Some people mentioned Fiverr and it is a good option since it is a competitive area, and people can find you easily, instead of the other way around.
Offering work for free is one of the few methods that some users have done previously. They might offer it for free on first order and then charge form the next order onward. It takes time to build your own userbase and nothing in this world comes without toil and hardwork. In the meantime one can keep improving and learning new skills in their field, in this case web designing.
Freelancing sites are one of the few places where every user gets a chance but it is a tough market to get into and building a reputation there will take time. Instead starting on a forum might give better chances because not everyone here is a designer, but there are many lurking.