Base cabinet toe kick.

Two things to think about, though:

(1) I don't recommend it be placed where you stand a lot -- e.g., under a sink or a cooktop. Cold feet in the summer and hot feet in the winter!

(2) You also might not want to put it directly under a trash pullout (or wherever you have your trash). It may not be an issue, but when we did ours, I wondered if the heat in the winter would heat up the trash. I don't know if it would have, but I figured better safe than sorry.

Ours is under our 36"W cleanup sink base, but it's off to the side on the side my DH does not stand at when he's cleaning up. I stood in front of the register once in the winter and my feet got really hot! [I usually prep on the other side of the Kitchen (with a prep sink), so I don't work at the cleanup sink much.]

Mine will be in the toe kick but NOT where I stand most of the time. Currently it is under the sink and I absolutely hate it.

Another vote for toekick register!

Base cabinet toe kick... off to the side WINS! Thank y’all

Toe kick.

Definitely not next to, or under, the trash cabinet. Our first house in the northeast had this "feature" and not one that should ever be repeated!