It's between seasons right now, so the perfect time to start up a new league!
There's many ways to make it work. The way the league that I'm in currently works is like this:
You draft a team of 4 Centres, 4 LW, 4RW, 6D, 2G, and 2 benched guys (that can be any position). You also draft a "farm team" of 14 prospects. This starts the first year.
Then, year over year, you select 10 from your main roster, and 10 from your farm that you "keep".