Working as of June 16, 2018.
So I was checking out the different parties that were going on around OurWorld and when I joined one of them I saw some people talking about a new flow game.
The game is called “William The Runner“
Step 1: Find “William The Runner”, it should be located in Arcade.

Step 2: Start the game and claim your first achievement (100 coins) and use it on HP, Attack, Regeneration and/or Attack Cooldown as your starter.

Step 3: You can leave it as is and start earning flow! Do not worry about losing your health in game, you restart back from 4 waves. Say if you were at 15, you go to 11th

The best way to maximize your flow gain is to fully level up your character’s HP, Regeneration, and Attack Cool down and that way your character can make it up to the higher waves. Higher waves means more enemies, which means more hits, which means more flow! It is recommended you only max out those 3 so your character can make it far, but not to the very end. If you maximize those 3 skills then you can go AFK and let the flow build up!
The amount of flow you get will also vary on your flow boost percentage.