Need advice

Im trying to make a 2x2 minecraft barrel block with extended storage capacity, I want to to take the vanilla texture at just upscale it to fit a 2 by 2 block barrel, Im incredibly new to Mcreator and ive been trying to figure it out for days, the closest I got to doing it was making a 2x2 model in blockbench and getting it into Mcreator with textures working, But the Bounding Box stuff wouldnt work at all, the front and sides would work but id be able to just walk through the block on the back top and bottom, Im at a loss currently, any help or tips for how to do this would be amazing.