Well, I've never seen anything complicated (never looked) but I sometimes do this when my lavender plants are blooming:
Take a whole bunch of the flowers (like a big handful) and put them into 80 proof vodka and let them sit for a day or two. Strain and add fresh flowers. wait another day or two, and if you feel like a really potent one, repeat until really potent. Eventually the vodka will be saturated and won't take any more smell.
I usually just do it once or twice.
Strain very well (use muslin or fine mesh) into a spray bottle. and viola! you have lavender air freshener.
The spray will smell like alchohol for the first 30 seconds to a minute after spraying, but the lavender will be all that remains after that. It's especially nice on a hot summer night, to spray your sheets with it, and wait a few minutes and climb in.

(Especially if you have mint planted under the window already, Like I used to. lavender and mint smell nice together. )
I suppose you could try this with other plant matter too, but I just haven't experimented yet.
Good luck.
Ian.