Honestly, interest checks always were something of an afterthought for me, mostly because my games are usually fandoms that already have an established fanbase.

But a pretty effective formula, I found, was posting the synopsis you have written out for the OOC, and format it to make it look pretty, as well as a rundown of what you're planning for the game and what you're looking for/ expecting of players. Add some pictures, format it to look presentable, and generally make it look like you have confidence in your idea, and it should drum up enough attention to get the OOC off the ground.