Although flashcards can help with rote learning, actually using words well requires greater familiarity with not just the word itself, but also how it interacts with other words.
For example, consider the word saw. The following sentences seem to be very similar, but they use different definitions of the term:
- I saw his bicycle. (Natural reading: I looked at the bicycle.)
- I sawed his bicycle. (Natural reading: I cut the bicycle.)
You can try looking up a word in a dictionary to get a feel for its range of meanings as well as some examples of how the word might be used in sentences. You can then try googling the word to see how it is used.
Note that search engines don't normally comment on whether a word is used 'correctly' in any given instance, so you might want to look at published works instead. Published work stand a higher chance of having been reviewed prior to publication. Ngram is said to be a large database of published work. At the bottom of the Ngram chart, there are links to the material used in compiling the stats making up the chart. You can click through to the broader context to see how the word is actually used in print.
After this, try putting together your own sentences and getting your teacher to look through them.
All this takes time, but if you want to recall the words so that you can use them well, you need to work out how they are used well.