Often times we get together with a group of people and want to enjoy rotating partners in an "open play" style, but unless there's a little bit of organization, things won't flow as well as they could. Paddle stacking can be fine for large groups when nobody is around to help organize play a bit. It's part of the culture of this wonderful sport. But it also leaves a good bit of room for improvement, especially in smaller groups.
With just a wee bit of management, there are some free tools that will help organize players (including signup ahead of time, if you like) keep things moving along smoothly, communicate court assignments, etc. I promise it's super easy, and people will have more fun because they won't have to worry about, or even think about, who should play next, who sits out, etc.
My favorite tool for organizing group play is Pickleheads, for a few reasons.
They're the official court information app/database for USA Pickleball, so in my opinion EVERYONE should have this app on their phone already.
They have created several options to organize play, depending on your preferences.
They make it easy to add people that join late, remove people who leave early, or pull someone out if they just want to take a break.
Players can sign-up, so you know when you've got enough, but not too many.
If you have players that are from a wide variety of skill levels, everyone will have more fun if they're playing with folks somewhat near their skill level. In Pickleheads, you can either sort players by skill (called Claim The Throne) or just go with a random start (called Gauntlet). Then just let the software create pairings based on the results of games as you proceed.
If you'd prefer to have everyone, regardless of skill level, mix randomly, then see my next recommendation called Popcorn.
If you have a group of players that are nominally the same skill level (or if you just want everyone to mix evenly regardless of skill), then the Popcorn format is great. It's designed to create as many unique matchups as possible
Pickleheads is my current favorite for organizing a group of similarly skilled players.
I know. I know. This one is gonna hit some people hard, but I'm telling you...in social play with a fairly small group (<20), timed games are much better than playing to a certain score. We've all been in that situation where the group is waiting to rotate players, but you have to wait on this one game that's stuck; nobody's scoring, and the game just drags on, holding up the whole group.
The solution is to play games to 11by2 (as is our custom), but also have a time limit. My recommendation is 15 minutes. You'll find that most games are done in under 12 minutes, so most games aren't going to hit the limit. But for the sake of keeping the group moving along, I recommend stopping play (regardless of the score), at 15 minutes.
Remember, this is a recommendation for social play, where the results don't reallly matter (no prizes or ratings on the line).