Hi !
Well, herniated disks aren`t really funny!
Don`t you know a physiotherapist/doctor (ostheopatic) or weightlifting-coach who has experience in this cases of back injuries?
I would recomend to search one who knows well about this!
So I just could tell you, what I would do if I we`re you:
First I would focus for 2-3 month on core strength. The rest of the body I would train light and on machines. Aim is to get the lower back and abdominals strong.
Second :
Include the basics back into your routine. Instead of incorperating back squats immediatily, I would choose front squats. Work on them hard 2-3 month. A deadlift variation I would also recommand, like Sumo DL or Rack Lifts. Depends on what DL's you could do with no harm.
Always start light ofcourse! Stretch your joints especially hams, gludes, quadriceps. Work your core hard.
Third:
If you think your're ready, start incorperating back squats and regular Deads. Start with Olympic Squats. Low bar Squats are ok if you can exercise them without trouble.
Well, not the holy grail, but that`s what I would do if I haven`t got any professional help.
Greetings,
C.