Just finished a snap-together stand for my 4 inch dashboard screen

I did something similar for a little round display I keep on the kitchen counter, and the friction fit approach is the way to go. Mine is three pieces instead of two because I wanted a wedge so it sits at a slight angle, and after a few iterations I learned the hard way that the tab corners need a tiny chamfer or they shear off when you press them together for the fifth or sixth time. One thing that caught me out was the material. My first version was PLA and it sat on a windowsill, and over a summer the frame slowly warped just enough that the fit went from snug to wobbly. Swapped to PETG for the frame piece and it has held shape for over a year now. If your hallway shelf gets any direct sun at all, worth thinking about before you commit to PLA. On the tolerance point, I found bumping the hole sizes out by a hair fixed the blobby first layer issue you mentioned, but the bigger win for me was slowing the print down on the tab sections specifically. My printer has a per-region speed setting and dropping just those areas made the fits come out consistent instead of a lottery between prints.

Nice touch keeping the dashboard simple with just temps and light sliders. Mine started as that and now it has a timer and a bin day reminder crammed in, and honestly the simple version was better.

Nice to see someone else hiding the ugly edges. Mine lives on the wall next to the front door rather than on a shelf, so I ended up solving a diferent problem: the cable. The USB lead coming out the bottom was the thing that bugged me most, so I built a channel into the back of my mount and ran the wire down behind the trim. Took three tries to get the channel wide enugh for the plug to sit flush, but now you can't see any wiring at all from a normal standing height.

One thing I'd flag from my own printing, since you went with PLA. My first enclosure was PLA too and after a summer of running 24/7 the area around the back of the panel went slightly soft and the case bowed out. Swapped to PETG and it's been fine ever since. If yours sits on a shelf in open air it's probaly a non-issue, mine was mounted flat against the wall with nowhere for the warmth to go.

I also left a gap around the screen edge instead of wrapping it tight. The glass on mine runs a couple degrees warmer than the room and a snug frame made the display look wavy in certain light. A millimetre of slack fixed it, might be worth checking yours for the same if you ever see odd reflections near the edges.

Out of curiosity, which orientation did you print the tabs in? I made a two-piece enclosure for a little sensor display a while back and printed mine flat against the bed, which looked tidy but left the tabs printing in layers, so every press-fit cycle shaved a tiny bit off the corner radius untill the fit went soft. Reoriented the second version so the tabs printed on thier side and they have kept their shape far longer. Also intersted in how the matte olive hides fingerprints, since the glossy black bezel on mine picks up every smudge in the hallway light.