Best bet would be a poured concrete pad, 4 inches thick, big enough for the lathe, and probably for you to stand on and walk around on. Compacted gravel under the pad. You could do 4 pier pads, and I would consider the extra work to about equal the extra cost of a full sized pad. I would not use the air conditioner pads. They also require a compacted base to sit on or they will settle over time. You might be able to get away with them, but dig them into the ground. Remove all loose dirt, add gravel, maybe some fine sand on top of the gravel to fill all voids, and add some water to help it settle, and a hand tamper will do an okay job, but to do it right, you need a compactor. You would need them to be level with each other as well. Again, the extra work for getting them is about equal to getting a full sized concrete pad. You can probably find one of those trucks that mix what you need on the spot, and they all probably have a list of contractors who can do small pads like what you will need. A 9 by 9 pad, 4 inches thick is one cubic yard of concrete. That is a lot to mix by hand, and the first part will be hard by the time you get to the last part.... I did residential concrete for 30 years.... Depending on the size of your shop, it may be reasonable to put the whole floor in. It doesn't hurt to ask. If it is covered and leak free, contractors love to have a job like this during rainy weather.
robo hippy