The clip-on stand hold the Steam Deck at 2 positions: 60-degree and 120-degree. In addition, it can clip on anywhere along the flat part in the middle of the Steam Deck, but will block some of the air intake/exhaust.

To prevent the clip sliding. Use electrical tape to line the inner-side of the bottom hook (of the clip).

P.S: I included the the .stl file for the bare clip, for those who want to remix the design for their own attachment.

Notes:

The stand needed to be printed flat and at (0.1 mm) for the best gear shape. But meant the round part of the pin can be rough in shape, and may need some shaving with a razor blade before it can fit into the clip.
The clip need to be print on its side for structural reason. It's thin-tall profile, make sure to do the tramming/bed-meshing and print the clip in the flattest area of the bed; and use a brim.

Lastly, the assembly will be stiff at first but it will loosen up as the mating surfaces of the 2 pieces get to know each other.