How do I get my apprentice to stop rushing cabinet prep?

What finally made it click for me was having my journeymen stop explaining and start making me say the steps back out loud before I touched anything. Not quiz-style, just 'okay, walk me through what you're about to do.' Every single time. Because the problem you're describing isn't a hands problem, it's a sequence problem. The kid can cut a scribe line fine when someone's standing there, but he's skipping the thinking part, so the cut happens in a vacuum. Making him verbalize 'floor first, then boxes, then scribe' sounds dumb but it forces the order into his head.

For the marking the wrong side of the line thing, that one's almost universal and it's mostly a knife-and-pencil habit. Teach him to mark with a knife, not a pencil, and to always cut on the waste side so a mistake eats scrap instead of the cabinet. Once he's nicking the actual workpiece a couple times because he guessed at which side to cut, the knife habit sticks fast. Pain is a better teacher than any explanation. On the level floor thing, I'd make checking the floor the literal first physical act of every install, like taking your boots off at the door. Level in both directions at each box location, written down on somethig before anything else moves. If it's a habit he has to perform before he's allowed to think about anything else, it stops getting skipped. The stacking trick you showed him is good but it only works if he checks the floor first anyway, so the floor check has to come first in his routine.

As for slack, a first-year guy who shows up early and eager is way ahead of most. The ones I worried about were the ones who stopped asking questions or got defensive when corrected. Six months to a year before the sequence stuff gets reliable is normal, honestly. Keep having him talk through his plan, let him make small mistakes on cheap material, and don't take it personally when it doesn't stick the first time. It took me two full years before I trusted myself on a scribe job solo.

What worked for me back when I was the green kid was being handed the same job over and over til it got boring. My boss had me set base cabinets in his own rental unit four weekends straight, no pressure, cheap boxes, and by round three I stopped rushing because the fear of messing up was gone. Repetition without stakes did more than any explanation. One other thing that stuck: I kept a little index card in my pocket with my steps written on it and crossed them off with a pencil. Felt silly doing it in front of the older guys but it kept me from skipping steps when I got excited.

Honestly the 'can't slow down' thing might fix itself once he's tired of redoing stuff. I was that kid, and what got me was my boss having me do the layout and marking the afternoon before, then no touching the boxes till morning. Gave me time to stew on it and catch my own mistakes with fresh eyes. Weirdly effective.

Also, is he rushed because he's trying to keep pace with you? Mine was. Once he told me to take as long as I needed and mean it, the quality jumped fast. Might just be a pride thing where he doesn't wanna look slow.

Update: took the advice about making him say the steps out loud before touching anything. Felt dumb at first but he caught his own mistake on day two, marked the wrong side of a line and fixed it before cutting. New question though, the overnight layout idea sounds solid but our installs are back to back most weeks. Any way to get that same breathing room when we're slamming jobs?