How do I Make a Floor Is Lava Map?

[Call24whem]

Remember to search before you post! But here it is!

How to make a floor is lava map

So many people have asked how to make one of these and ive decided to make a guide about it so here i am, if you are wanting to make it to where you can build thats not added in gimkit creative yet. Any way here it is. STEP ONE STEP TWO CONCLUSION Lemme know what difficulty my first guide was: poll