How would you setup a multiple block model from a custom block?

ISSUE: 

The model is two barrels, one stacked on the other with a slight rotation, then it has a ladder leaning on it. So it adds storage with GUI (already done), as well as a climbable feature. Image below. 
( https://postimg.cc/qN0r61Jn )
How do I implement this in game as intended? Is it even possible to do it this way? 
If not, how could it be done utilizing the storage and ladder aspects. 
Thank you to anyone willing to help :)

NOTE:
I am not talking about placing 1 block and then having it call other blocks to form something (although if this is an easier option or more realistic I would like to learn), I am talking about placing an entire model with just one block. 

I don't know how to write code and I am not fluent in the program, I do this for fun and to challenge myself. Any help is greatly appreciated. Thank you.