He most likely took a lot of time and effort to build it. As with all "popular" places, it takes a lot of scripting and hard work to build a good place. The exact way that anyone built a script is unknown unless it is a free model, he tells you how he built it, or you hack to steal his place; which is nearly impossible, against the TOS, and will get you banned.
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Make a humanoid, insert a follow script, then insert a lava script.
Use one of Anaminus's Script building games.
learn to script or use free models
With a little knowledge of how to script, you can add your own commands to a VIP commands script. If you don't know how to script, you can learn by following the tutorials on the Roblox wiki. There are also numerous fan-created tutorials on the Internet which you can find by searching Google for "Roblox Scripting Lessons".
To put a script into something, you have to go to roblox studio and open the dicovery directory thing, click the double click the thing u want it in and make or type a script there. U can also use script builders to see if the scripts work