For my vertical 60 gallon unit, I poured a slab 6 inches thick, and about 2.5 feet square, with a plywood square form, and poured the concrete on top of a sheet of plastic, so it would not bond to the floor below. I set anchor bolts into it while wet, located for the four feet of the compressor. After it cured, I removed the forms, slid it to where I wanted it located in the shop, pryed beneath it with a flat bar and then a big wrecking bar to get it off the floor a couple inches, then slid in four hockey pucks, one under each corner. After lowering it down onto the pucks, I mounted the compressor on top of it using the four anchor bolts, with a pc of rubber belting above and below each foot, and a fender washer on top of the rubber above the foot, then a nylock nut lightly. The features of this work gave me a base that wouldn't tip over, a compressor that could not be stolen easily, the base could be moved if desired, no vibration is conducted into the floor for greatly reduced amplification inside and outside the building, a compressor that is raised up a good 8 inches for easier access to the water drain.