How do I create a real time player base building and crafting system?

Building construction system. Specifically I want players to be able to put walls , doors etc up as holograms Unreal Engine 4 | "The Forest" like gamplay | Building system | Construction - YouTube then build it with materials in there inventory .

I want to change the building to be able to be placed and snaped on top of one another like - YouTube

In the end specifically , I want my players to have a hologram of the building piece they want to use lets say a wall, then place the holograms down like in your blueprint but make it so they can be destroyed after placement if one chooses to, giving my players the ability to pre make there base / home visually .

Well you would need a pickup system and inventory system for 1.
The placing of a object would be done using two actors(the ghost actor[which is the white transparent building] and the fully compete model) [this is basically what you want Unreal Engine 4 Simple RTS Building Placement - YouTube]
The UI is rather basic using a 3d widget based system.