Get the non-3D-printed parts.Acquire the 9g servos, Bluno Beetle, Mobile Battery Booster, and find a phone you want to use. The phone needs to support Bluetooth LE (Bluetooth V4, I believe).
Use a [very] hot air gun, reflow, or heated wire to soften the holder's fingers and bend them round some wood. Remember to leave enough room for the phone, a phone case, the heads of the screws, and a little space to insert and remove the phone.
Design 1: Don't make the viewing tube too big... you want the phone to be a bit bigger than the hole.Easy to adjust lens distance to phone - lenses are mounted on separate piece of just the right height and folded to width for stability.
Design 2:Requires a phone case that straddles the back cardboard edge. You can't adjust the distance of the lenses to the screen afterwards!Trickier to make robust. I was lucky my phone case squeezes in. Otherwise you might need to put a lid on it to...