Suggestions using OPK at work/office

Jenn
Hello everyone! I'm 36 and TTC for our first. It's been 6 months. I hadn't been getting any surges with my OPKs and had been doing them with FMU. I've been reading a lot of posts and am seeing I should start doing them twice a day and between 11am and 2pm. Is this correct? (and why if you happen to know, just curious as instructions say first thing in the morning)
The real question is, how do I attempt to take an OPK discretely in a busy office building? I'm perplexed. Can't exactly pee in a cup or wait in a stall for 5 min. Suggestions/experience greatly appreciated.