Which is correct grammar,
- Farming consists a lot of manual work.
- Farming consists of a lot of manual work.
Also, is is ok to write 'a lot of' instead of 'lot of'?
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“Farming consists of manual work. How much manual work? A lot.”
This is the better option, and is something a native speaker would say.
“Farming consists of manual work. How much does it consist of manual work? A lot.”
This is slightly awkward, but still correct. It has a slightly different meaning, however: that farming consists mostly of manual work (but there are other kinds of work too).
"A lot" is commonly used in informal speech with the meaning "often".
The phrase is often placed at the end of the sentence.
Placing the phrase directly after a verb may also work.
For certain verbs or prepositional phrases, it may result in coupling which will confuse the sentence's meaning.
In other cases, it may result in a sentence for which the meaning would not be instantly decipherable by native English speakers.
Regarding the OP's question: