All my friends can do it, and they tell me to jump-crouch little to the left. What is the RIGHT approach?
Your friends are correct - just jump-crouch with the correct orientation and you will be able to get on top of the container. If you are not yet used to using the technique, it can sometimes take practice.
At 1:12 in this video the Youtuber demonstrates how from the opposite side, but it can be done from either.
You have two options... learn how to crouch jump (useful quite often) or make a binding that does that for you (yes, it's legal).
If you want to learn how to crouch jump you need to time it properly. Press crouch to soon and you will miss the jump. The best way to learn it is to open a single player game (with or without bots) and just go on that map and do it until you make the jumps.
Use a bind:
alias +cjump "+jump; +duck" alias -cjump "-jump; -duck" bind space +cjump
With this bind you will have no problems managing those jumps anytime anywhere.