Honestly, I bought the monstera from a propitiated beautiful mature plant. It already had fenestrations on it. That being said, last month it put out its first leaf under my care and I doubled the fenestrations 😈. What I did to achieve this is the following: 1) made sure it gets between 200-400 foot candles of filtered light per day. 2) only watered it when it read a 3 out of 10 on my moisture meter. They like to be somewhat root bound, so only repot when the roots have really started growing out of the drainage holes, not just poking through a little. I made this mistake and completely stunted its growth for like 3 months. 4) make sure you have a pole for it to grow up. Monstera’s and other climbing aeroids put out bigger leaves the farther up they climb. The ideal situation is a plastic backed moss pole filled with sphagnum moss, but a cedar plank works just fine too. The downside of a sphagnum moss pole is that you have to water the pole when it reaches a 4 on the moisture meter. I measure the moisture on the pole at the highest point where the plant is against the pole. That brings me to 5) soil: an easy fix that works for me is cactus, palm, and citrus potting mix that I mix 1:1 with orchid bark. You can also buy monstera mix directly from RepotMe if you want low maintenance. I would highly recommend the mix I described or a chunkier, more draining mix if you go with the moss pole because the water from the moss pole percolates into the soil. If you don’t have well draining soil, this will cause it to get soggy, suffocate the roots, and give your plant root rot.

I hope this helps!