Sage and rosemary can easily be layered. In fact, my salvia new plants have developed roots in 2 months.
Just find the longest stem and add some free-draining moist compost and push the stem(s) into the soil and bury them. Water, water and water. That's what I did and I have now several new plants. Salvia / sage roots very readily. You can take cuttings with 50/50 compost and sand.
I would do the dame with rosemary but scrape the underside of the stem. If you can, look out for a hugging rosemary. They are now reduced to about £1 and it won't expose horrible looking bottom stems and the hugging covers horrible spots. A very elegant scented plant. You can use a stone to weigh down the layered stem.
Hope it helps. Thyme I haven't got, so cannot comment.