I have been reading your articles for quite some time now. I have made good gains with my routines and I work out every other day, but I have a bad problem with my forearms.
The belly of my forearms is really bad, although the top outer part near the biceps is OK. I also have thin wrists. Is this a factor?
The forearms are worked in almost every exercise we do in bodybuilding. Some people get enough development just from this all-round work.
The size of the wrists are not a reliable indication of how big your forearms can get. The amount of cell allocation is the key.
Your problem is a back-to-basics case. I suggest you start every workout with seated wrist curls using a barbell. Go for 5-8 sets of 10-12 reps per set. Hold the elbows in close, forearms resting on the bench and raise and lower hands with an even cadence (rhythm).
Do not allow the hands to unfold at the bottom of the movement. This works the fingers not the forearms.