You can put it on one, but you should not. A flat stone only touches the raised points between the scallops, so it grinds the teeth flat while leaving the recesses untouched. Do it for long enough and you have converted a serrated blade into a poor plain edge.
A serrated edge is a series of concave scallops with points between them. A flat surface cannot enter a concave one, so all the abrasion lands on the points.
The points get shorter, the recesses stay dull, and the edge stops sawing without ever becoming a proper plain edge either.
After sharpening the scallops with a tapered rod, you lay the flat back of the blade on a fine stone and take one very light pass to remove the burr. That is the only correct use of a flat stone on a serrated edge.
One pass, minimal pressure. Anything more starts grinding the flat side, which destroys the single-bevel geometry.
A tapered ceramic or diamond rod. One tapered rod covers several serration sizes because you simply seat it at the depth that fits.
See how to sharpen a serrated edge for the method.