There are many methods, as I'll explain here.
Flesh Crawlers
Pros
- Easy to kill
- No slayer requirement
- Can be done with 1 defence
Cons
- Far from bank
- Usually packed.
Chaos Druids
Pros
- Drop a lot of herbs
- Easy to kill
Cons
- Wilderness area of taverly dungeon
- Packed
- PKers
- Far from a bank
Cave Crawlers
Pros
- Very low level, 1 hit a lot of them
- Not very busy generally
- Close to lummy RFD bank.
Cons
- 10 Slayer requirement
- Can poison
- Bit longer bank trip if not started RFD.
- Drop low level herbs generally
Aberrant Spectres
Pros
- Never busy
- Multiple Locations
- Drop higher level herbs generally
Cons
- 60 Slayer requirement
- High combat needed
- Protection prayers are essential
Sorceress garden
Pros
- Can be done at low thieving
- No combat required
- Easy once you get the pattern right
- Bots don't affect you
Cons
- Higher thieving = better herbs & quicker herbs
- Bots can cause lag
Hope I helped
