Well.............if we're going for simplicity and functionality......this would be the best way.
1. Create a new layer. Fill with white, set opacity to 40% to 50%. Go to LAYER > CREATE CLIPPING MASK (or hold option/alt key and maneuver your cursor between the two layers you want to clip, the cursor will change then click).
2. Choose your text tool and type a letter. Position and size doesn't matter (this can be changed at any time).
Double click this layer which opens the layer styles. Under ADVANCE BLENDING, set your fill to 0 (zero) and in the KNOCKOUT flyout menu choose SHALLOW, click OK.
Go to LAYER > CREATE CLIPPING MASK (or hold option/alt key and maneuver your cursor between the two layers you want to clip, the cursor will change then click).
Done.
I you want to move the letter..............choose your Move Tool, highlight the text layer and move.
If you want to change the letter's size...........hit Cmd/Cntrl + T or you can double click the letters thumbnail in it's layer and make changes using the Character panel.