The Problem - Weak Shoulders
While equipped benching can pretty much be summed up to good technique and huge tricep strength, to have a big raw bench you need to have killer shoulder strength. Weak shoulders hold back benches everywhere and can be one of the most stubborn areas to grow. However there is a solution!
The Fix - Overhead Press Anything and Everything
Isolation movements such as lateral raises and fixed presses are great but to build brutal shoulder strength you have to overhead press, and overhead press A LOT.
People don't train overhead pressing as much as they should mostly because, well... it sucks. You either love it or you hate it. I happen to hate it and its one of my weakest lifts. I've been prioritizing it much more as of late and my raw bench is thanking me
Standing strict overhead presses with a barbell is probably the most effective exercise to build strong shoulders. It doesn't end at the barbell though, you can use dumbbells, kettle bells, even strongman logs to press overhead. Each gives a slightly different stimulus that can break you through plateaus and onto new strength levels
In my quest to build a strong overhead press I would even press loaded kegs overhead. With a heavy enough keg this is brutal and you also need to clean the weight into position making it a great overall body strength builder and power developer
The answer is clear! Find heavy ass things anywhere and press them overhead! The more you overhead press the better you will get at it and you will soon see major growth and strength development