Create a new class that extends "Block" class and you need json for it in resources/assets/modid/blockstates directory and resources/assets/modid/models. You can generate json for it using a tool like misodes model generator. Here, atleast, are blocks explained at forge docs.
Don't forge to look at vanilla code, like Magma Block is a good reference if you're trying a "green fire block".
Modid should be replaced with your actual forge mod namespace!
Hi my game crash with exit code 1 forge 1.19.2 java 17.02 no mods installed, i tried with forge 1.20 and same error. Vanilla version function. This is the link for the log of launch of forge 1.20 https://pastebin.com/jxqTeZkN