As well as one white Frisbee, needed for the jack, each player will need four Frisbees marked or coloured in such a way as it can be identifies alongside those of the other players.
Played in a large park area where you will not interfere with other park users, the idea is to get your Frisbee/s closer to the 'jack' than your opponent's Frisbee.

Place a towel, or mat, on the grass giving you a place to 'bowl' from.
The first player to bowl is decided by the throw of a coin.
The first player stands on the mat and throws the 'jack' as far as s/he believes that s/he has the best chance of getting closest to it.
The opposition player stands on the mat and attempts to get the Frisbee closer. Continue until all eight Frisbees have been thrown, then, taking your mat with you, walk down and check your score.

One point is scored for each Frisbee that is closer to the jack than the opponent's. (that is, if the opponents Frisbee is the third closest to the jack the closer player scores two points.
Set up your mat and repeat the process (in the opposite direction) with that player that was closest to the jack leading off. Easy peasy !You can play to the first player to reach twenty one or play a set number of 'ends'.

If you want more than two players involved you can have two, three or four players on each side.In these games a pair of opposing players play their 'end', followed by another pair, etc. with the result being drawn from all of the Frisbees thrown.
In threes or fours you would be better off just throwing two Frisbees each.