I did my workouts before at two different convenient schedules:
1) An hour before my work schedule. I showered from home, used the sauna and showered again after my morning exercise from the gym that make coming to work feeling so pumped up and alive. Most gyms have early opening hours. You may also adjust your schedule reporting to work with your boss and cover for the missing hour later in the day. If you can set this as a fixed schedule, then it would be easy for your boss too to not expect you to be at work around the time you are at the gym. I had preferred this morning workout; it helps coming to work with a positive energy that would last the whole day; OR
2) Leave from work before the gym closes giving you 1 hour at least to do your exercise. You can shower in the gym or when you reach home and get some good rest. The disadvantage of an after-work-workout is that the gym would be full and busy. With all the day's work, you could tend to get lazy to workout and just hurry home and watch t.v.
We had executives who used their hour breaks at work to work out and lunch-in in their offices. You can do this too. You will need to get off your seat anyways and give yourself some fresh air.