Help related block placement

Would someone be willing to provide me with a detailed explanation on how to create a block placement system by utilizing the information presented in the following video: Roblox Bedwars Block Placement: A Simple Approach To Recreating It! - YouTube? I kindly request this information to be as thorough and clear as possible.

What have you tried and which part are you stuck on? Or do you just need some pointers to get started? Creating the “hidden cylinder” and making it follow the player is a good first step.