The most common slot tournament format consists of three rounds of play with the lowest score dropped. Other structures include the best three out of four scores and twin tournaments, offering players two tournaments in one weekend with two chances to win.
The chance to win big for a small investment: since slot tournaments can attract a large number of players, this also means that many buy-ins contribute to the prize pool. Considering that everyone has an equal chance of winning, there's a good chance you'll make a tidy profit on your investment.