In the 16th & 17th centuries the information below would have you branded as a minion of TheDevil. Why?,?

The basic principle is easy: put the herb in the oil, and wait.
If you are bothered by herb particles in the finished product, you can
use a tea egg or a small bag of muslin or nylon suspended by string in
the bottle, and remove them when you find the fragrance strong
enough. This requires a bottle with a wide opening. If you don’t have
such a bottle, you can strain the oil in a wire-mesh tea sieve
instead. If you aren’t bothered by herb particles, you can often leave
the herb in the oil until you’ve used it all up. This works
particularly well with antiseptic herbs like peppermint, but can in
other cases make the oil go stale.

The time it takes for an oil to become pleasantly fragrant depends on
the herb and the oil, what you consider pleasant and the conditions
you keep them under. You will have to experiment with concentration,
stirring, and time to find out which works best under your
circumstances. With some herbs crushing can speed up the process.
Seeds like fennel are among those. Many herbs vary quite a lot in
strength depending on a range of factors, so sometimes you will have
to adapt your recipes. The best thing is probably to develop your
intuition with regards to herbs. As a rule of thumb, two weeks to
three months should be adequate.