When doing 60/60 interval training, what pace should the slow 60 be at? Can I walk the slower 60 or does it absolutely have to be a jog?

Depends. Depends on your program and goal. How fast is the other 60? Many programs heve a walk element in there, especially if you are beginning the program. See how you feel. If you are sprinting the other 60, then either will work. If quicker jog, then take the rest time, and walk. You can always move it up to alternate as you feel better and get stronger. Good luck.