I use the print paper and the elect tape. Roll them sokkers right up, carefull tpape em over and round...they work for me.
I like the Idea that the white inner surface will provide a nice room for the pairs of LED?LDR"s, and that I have plenty of print paper handy at all times.
I start with rolling the LED making the paper into a cone that gets bigger enough to just let the LDR [utilizing the legs and round of the LED to kinda hold the paper] almost, or kiss the LED...I'ts not that hard for me to work with, and the LED 'seem's to be pointing toward the center of the LDR.
My LDR's are about twoice the diameter of the LEDS at the widest points.
All the explanations i've read [associated schemaatic text etc.] show the use of shrink tube...either way would be fine for me...one of the main objectives is to seal out any ambient [outside] light from the each pair...and alignment...though light has a way of finding it's way...
You want to get good variability of resistance of the LDR and want it [I think ] usually to go to low Resistance [?] deppends I guess...here..obviously I'm not the one AFAIK