I pray at the corner and during lunch and break time. So if the boss have a problem with it...well..he can have problem with it. If he wants me stop or else..I will give him resignation and leave.
I'd say try to work your break times around the schedule of prayer, or ask someone to fill in for you for a few minutes until you return if that is allowed. People are generally considerate and supportive. You can use an empty office, room, or corner.
You can also just ask your supervisor for accommodation. By law in the US, employers have to allow religious accommodation for their employees.