This had me bugged. Shimano introduced Hyperglide front, and that would call for timed rings. So I decided to check the tech docs, and sure enough, the inner ring does have a timing mark. (at least in Ultegra, which is the one I checked).

I don't know if others have timing marks, but the lack doesn't mean that timing doesn't matter. Lacking a guide, I'd either time them with the chain as I described earlier. Or if Shimano is consistent about marking near a bolt hole, put the mark near the arm opposite the crank (not the timing mark which goes to the crank arm).