nuances - How can I differentiate between feet and legs?

Feet are 足, and legs are also 足.

Is there a word or method with which I can easily talk about one and not the other? And if not, why is there no word for feet in the Japanese language?

Caveat: I know that one can just use フィート but that feels so very not Japanese...

Answer

Is there a word or method with which I can easily talk about one and not the other?

A short answer is that there is no simple way. If you have to talk specifically about foot but not leg, you have to explain it such as 足{あし}の足首{あしくび}から先{さき}の部分{ぶぶん} (the part of leg which is below ankle). Similarly, you have to exclude foot, you have to explain it such as 足{あし}の足首{あしくび}より上{うえ}の部分{ぶぶん} (the part of leg which is above ankle).

There are two kanji for あし: 足 and 脚. Sometimes they mean different parts of human body, in which case 足 means foot and 脚 means leg (including thigh but usually not including hip). But this is not always the case, and in particular 足 can also mean the same part as 脚. My personal impression is that using 脚 for foot is rare.

As technical terms in medicine, 足 always means foot, and 下肢{かし} means lower limb (which is a little broader than “leg”). The precise meaning of “leg,” which is the free part of lower limb (the part of lower limb that we can move by will), is called 自由下肢{じゆうかし}. But 下肢 is a formal word and not usually used in a daily conversation, and 自由下肢 is completely a technical term and at least I did not know the term 自由下肢 at all until I looked it up just now.