A Ikea Skadis shelfs with external hooks after the idea of another thingiverse collection (https://www.thingiverse.com/thing:2853261, IKEA SKADIS Collection (easy print / tight fit)).
The hook allows a bigger wall thickness so that the prints are stable enough with PLA. The shelf itself does not dangle /warp over time, which is what happened with the original collection for me.
The author marked this model as their own original creation.