Since you are specifically allowing a for a lenient DM, some possibilities spring to mind, all requiring DM approval.
Acid Splash is a cantrip that you can cast over and over again at no resource cost. Whether the acid produced is strong enough to dissolve flesh, yet weak enough to leave the bones is something to discuss with your DM.
Alternatively, consult an alchemist for a type of agent that will work, apparently a strong base instead of an acidapparently a strong base instead of an acid. that will work. You'll likely need a prep tank though, so it's not a good on-the-fly solution.
The dividing line between zombie and skeleton is really the amount of flesh. Bones with a few tendons would be hard to justify as a zombie. If you practice, you might be able to quickly carve enough flesh away to qualify. If your DM rules leniently, this might even be a task that can be given to an Unseen Servant.