At 11:38 into the 13:49 minute video his case does already have a hole (the last 30 seconds is just a screen shot), so I assume that the A1200 cr version is the same as the A4000's connector in plastic. Under that assumption, you need an "L-shaped" piece of metal or plastic with a cut-out on the short side to attach the hex mounting screws to and then the long side would screw or glue to the inside of the case. For those of us who refurbish Amigas, this would take a few minutes to shape with metal shears, a Dremel tool, or scissors; for a beginner you would need to find someone familiar with the dimensions and materials and have one made for you, so good luck on your search.