Well I have a discord server where I mainly host them. You can find the link to it on my FA as an easy access to it.

Though how I do it is I choose a prompt for the tournament, I do one each season (to lower the risk of burnout), and I start it up when the season comes around! I will sometimes ask people in my server for suggestions for pokemon for the tournament, get all of them chosen, and then voting begins for each stage of the tournament. Then after the votes, the winner of the votes gets a bonus to their dice and the pokemon battle it out using D20s, best of 3, and it continues like that till the finale where it changes to best of 5.