I recently stumbled across the below video regarding how to conveniently hold a motor in the “channel” of a pinion press such as the Slot.IT (TL01) and NINCO (80201) presses. The video is for a SlotingPlus press (SP140004), but the trick would work for any “channel-style” presses.
Simply – get some 1, 1.5, 1.75 diameter O-Rings – what can fit snugly around the body of the Press. These are used to hold in the motor as you fumble around putting the pinion onto the pinion block or the dual-pin press.
https://www.professormotor.com/product-p/sp140004.htm