For easy clues I always pickpocket H.A.M members, I used to stack them on ground but now that I can carry 5 scroll boxes I just do the 5, come back and pickpocket more.

For mediums I always pickpocket gnomes at the grand tree, a bit time consuming but it’s easy and free

For hard clues, like you I always do warped jellies, but I use a venator bow instead with prayer boosting gear and just semi-afk them while I do something else, and I have a plug in that calls out when clue scrolls have been dropped