Yo as the title says:

I have a really hot colleague that recently broke up with her boyfriend. Now I know that there might be some potential there as she tends to smile alot and be overly friendly when around but then again she is also very very professional and doesnt usually talk much about anything else than work.

I will be switching departments soon (will not have any contact anymore) thats why I thought I'd give it a try.

How do I slowly make an Approach?