I recently purchased a new tablet with a rather large screen (12") and I immediately noticed how difficult it is to hold it in my hand for a long time compared to those of the past when I use it comfortably seated in an armchair both because of its size and its weight of over half a kilogram.
The cover, although foldable into a triangle, is not very useful if you do not place the tablet on a stable surface, so an alternative solution was needed to be able to hold the screen effortlessly in your hands.
I therefore designed two handles to apply to the cover when it is folded into a triangle that help me with this purpose.
I would like to point out that the cover, when folded, normally takes the shape of a triangle with two sides at 90 degrees: these are the two sides to be inserted into the slots of the right and left handles. The hypotenuse of the triangle, however, remains free.
The handles are designed for a cover whose legs of the right-angled triangle are respectively approximately 60 mm and 50 mm and with a thickness of the cover of approximately 2.2 mm.
If your cover has different dimensions than those indicated above, the handles will need to be duly re-proportioned (in scale) before printing them in 3D.

Furthermore, before creating the model with the handles, I created two corners with similar characteristics whose purpose is to block the flaps of the cover and make it a single body in order to significantly improve the support of the tablet on stable surfaces. I also attach the files for these preliminary corners.

I used PETG with standard settings, without any printing support and with a 15% infill.