Hi-hat foot technique is usually built around two basic motions: jazz motion and rocking motion. In most musical situations, the left foot works as part of the time feel. In both versions, the heel usually marks beats one and three, while the toe marks beats two and four. As a result, we get a closed hi-hat sound on the even quarter notes, which is common in jazz drumming.
Jim Chapin’s is one of the classic books where this skill becomes useful. I recommend counting time with the left foot not only while playing grooves, but also while playing fills.