Using scrap material the same thickness as the PCB you will be printing on. Create a fence bracketing the upper and left edges of the board and secure them down with tape.

Index PCB firmly into corner formed by the two scrap boards. Lay Proto stencil on top of board and using a loupe or magnifier, align and tape foil down along upper edge only.

Print solderpaste onto PCB. You may choose to tape the board down to prevent any shifting during this process, but avoid taping near fine pitch components as it may affect the print.

Lift and remove printed PCB and load the next board to be printed.