My basic cell is a bit different- but then, I'm pretty sure I'm building something closer to a very strict vocational school than a prison.
Yup- showerhead, toilet bed, tv, phone booth, these cells are like a really compact discount hotel room. The only modification I'm thinking of making is moving the toilet atop the drain between the shower head and bed- that way I can get it within a 2x3 area for a Cell, while leaving the shower head to become a small Shower. I was wondering why my prisoners would just stand around during the Shower portion of my regime, then immediately start using it at Free Time; I'm guessing that not having an area designated a Shower room is the cause.
I do blocks of 10 cells, separated off by Jail Doors. In theory this would be very helpful in a lockdown situation- but I've yet to actually need one. This also separates each block into a sector for Deployment purposes, and I could easily put a metal detector every block or two to cut down on contraband. Generally though I tend to try and bottleneck the problem at the source.
Because the map is wider than tall, I try to keep my construction modules horizontal. I set up this design for my latest small prison; the canteen will feed 80 prisoners, and the kitchen can easily keep up with two meals per day with four cooks. I've made the decision to designate the Kitchen as Staff-Only, to cut down on the amount of contraband the prisoners have access to. I tend to have a guard patrolling a three square path by the door, to immediately catch anyone with contraband. Honestly I tend to get more alarms from prisoners coming in than going out.
My administration block is very utilitarian, and tends to get shoved off to a corner of the map next to the road, with the only door leading out. The only visitors are Janitors, so my Warden, Chief, Accountant, and Foreman can just wander in circles all day, ignored.
The infirmary doesn't get many visitors, if any, so I've kept it pretty small. I've shoved the Psychologist's office in here because it makes sense in my head to have all the medical stuff in one place. Because the morgue leads out to freedom, I've tried to keep several layers of staff doors and a good bit of distance between them to prevent escapes. The entire area is Staff Only, since the only visitors to the infirmary will be under guard escort, so again I've tried to cut down the amount of contraband available. Honestly I didn't try for space efficiency here just because I had extra room, and I allowed myself to go with some aesthetic choices. I like the hallways three wide so I can center the door. I could have easily compacted the morgue down to two slabs, but again, I didn't need to with my overall layout.
The maximum workshop options, as I can figure it. Three tables easily handles the necessary sheet metal and completed license plates in my daily shift, and one room can employ two cell blocks. I could have compacted the work stations down further, but after watching the pathing on the prisoners and workers, I decided an open grid design would work best for getting pieces from place to place quickly. Again, a metal detector at the door to catch contraband. It's worth noting I keep normal doors on workshops and the canteen to cater to the prisoners' freedom need.
All my other rooms are designed according to available space and security. I use Janitors rather than a cleaning cupboard (my prisoners only cleaned the cupboard once and then just wandered around, anyways- and again, less contraband), the cells' deluxe accommodations means a common room falls into disuse, and I could probably even forego a visitation room thanks to the phones- it would reduce the contraband, micromanagement of opening staff doors, cut opportunities to escape, and be more efficient. My laundry, yard and storage rooms tend to be whatever's available around the rest; the utilities are usually shoved into a storage room or in available gaps between buildings. My most frequent offenders are prisoners carrying contraband, who end up shoved back in their cells, but for solitary I'll usually have some space between disconnected cell blocks where I can hook up a toilet and add a door.