The Pre-built PC I bought on sale only has 2 PCI express slots and the graphics card takes up two. I needed a USB 3 expansion card so decided to move the graphics card with a PCI express riser extension (this is the 9cm, I can't find the 25cm I used here).
The card is held in place with four 3D printed corner mounts that are screwed into several layers of glued MDF. The MDF is bolted to the case's original side panel. The tinted window has been removed. I was lucky the power cable reached.