I'd like to cut back on my kratom use as well so I feel your pain. It's getting too annoying having to make sure I don't run out, plus the varying quality among different vendors makes for some uncomfortable/unplanned withdrawal symptoms.
It all depends on how quickly you want to stop. You could cut back by one tablespoon per day, one gram per day, one gram per week, etc. Supplementing with loperamide or DXM (in low doses) could help if the withdrawals are bad. But both of those can cause dependence as well so don't overdo it!