not having a custom cut screen protector for a small touchscreen phone I cut down and fitted a left over one from a previous phone.
Step 1: Mark and Cut
leaving BOTH protective foils in place on the over size screen protector. position for the best fit and using a fine tip marker that draws on plastic mark the outline you need to cut. then using a good pair of scissors cut to fit.
Step 2: Alignment Assured
I adapted this step from the fitting instructions for a screen protector for a tablet. For preferenc I would have used paper decorators masking tape, but as I didn't have any I cut the sticky strips off 2 sticky notes and used that instead.(it is important to use a low tack adhesive tape that will peel off your phone's case without leaving a residue) Place the tapes over hanging one long edge of the protector on the remove second side. (preferably the uncut edge)
Step 3: Clean Polish and Fit
clean the screen of your phone. check that the peel first side is going on the screen LEAVE it in place. position the protect on the screen secure the edge with the tapes. The tapes now keep the position correct as you hinge the protector up peel off the foil and hinge it back in place.
Step 4: Finishing
having pushed any air bubbles to the edge remove the second foil. get rid of any remaining bubbles and you're done.