The Sandbag Back Squat is one of our top 3 strength building exercises, the others being the Sandbag Deadlift and the Sandbag Overhead Press. At Sandbag Fitness we perform it (with just a few small adjustments) as you would with a regular Barbell. The major variations are based around working specifically with the bag as opposed to the bar. With that in mind, you could use the sandbag back squat as part of a modified Starting Strength or Wendler 5-3-1 programme.
The Sandbag Back Squat is the squat variation that will allow you to lift the most weight - it is therefore a vital component for building strength. However, we also include Sandbag Front Squats, Sandbag Zercher Squats, Sandbag Shoulder Squats and Sandbag Bear Hug Squats in this programme for the other benefits they provide.
Images and text from The Complete Guide To Sandbag Training