Team slots enable players to save multiple teams at the same time for later use - for example, if a player wanted a team that mainly used skulls but also wanted a team that mainly used troop abilities. These slots are accessible from the Troops menu.
A team slot will store the troops in the team, the banner attached to that team, and the team's name.
Players start with one team slot and unlock additional slots every 10 levels up to a max of 26 slots (so level 260 is the last).
You can earn an additional 20 team slots by increasing your VIP level. You receive one team slot for each VIP level you unlock. So you can have up to 46 team slots in total.