Since there is already a One Piece book club thread in existence, I might suggest @-mentioning the original creator in the home thread to see if they’d rather you take over and pick up where they left off, or be okay with you creating an entirely new club from scratch. Sometimes forum users have emails turned on, so even if the op isn’t active anymore they might get an email notification and come back to answer. If they don’t reply after a week or so, I would think a new club might be okay to start?
For making a book club, check out the holy grail thread on how to do it: Tips for Running a WaniKani Book Club
And it doesn’t hurt to browse some of the other clubs for inspiration 
Master List of Book Clubs
EDIT: Looks like you’ve already tagged them! Now all that’s left is to wait ^–^
I also noticed that they were making one thread per chapter (?) which could become a bit excessive very quickly. If you want to group volumes together, I decided to group my threads by arc for the NARUTO book club which you’re welcome to consider doing as well (shameless self-promo ahaha)