I joined a friend's game, and tried to get the achievement. I managed to stand on a barrel for more than 3 seconds. It popped only after I left his game and was in my own game. Jumped on a barrel (not even 3 seconds) and then it registered and popped.
A good spot is across the Abyss Bar in the Space Rig, in the corner to the right of the Jukebox (facing the Jukebox). There are some chairs and a table. You can squeeze/kick a barrel in between the gap, and try to jump on it, without all too much glitching-barrel-action.
Another good option is kicking a barrel in the drop pod (it’s also another achievement which requires 4 barrels in the 4 seats). Once the barrel is in the seat, its way more easier to stand on it.