Clowns aren’t sexually mature until they are 2+ years old. Once they’re old enough, put a clay flower pot or piece of tile for them to lay eggs in. You’ll need to culture rotifers and phytoplankton (or buy it). You’ll need a hatch tank and a grow out tank. It’s definitely not a simple process, but there is lots of info available.
They need to mature then you need to feed them a lot of quality foods to get them in spawning shape. Once they lay you need to collect eggs for a separate grow out tank and grow phyto and rotifiers.
Clownfishes - Kindle edition by Wilkerson, Joyce D., Thomas A. Frakes. Download it once and read it on your Kindle device, PC, phones or tablets. Use features like bookmarks, note taking and highlighting while reading Clownfishes.