I know this topic is common on here, but a lot of the threads are old. I just bought a used, only used a couple of times, pair of Ariat tall field boots. I own a pair of Ariat zip up paddock boots that are a size 7.5B and fit perfectly, so I thought the 7.5B would fit the same for the tall boot, but it is actually a little bit big on me. The calf and ankle fit fine, but I wanted to know if there was someway I could shrink the actual foot size of the boot. I thought maybe the bathtub method might work, but I’m not quite sure. Dover’s website said something about using air cushions, gel soles, or padded footbeds to help make the shoes size fit better. If the Bathtub method won’t help, does anyone know of any inserts that will help. I’ve tried looking up inserts for making the shoe size smaller, but they go in the front of the shoe and I need the insert to bring my foot forward and not back for when I ride. Any input would be very helpful!!
I use inserts for lots of shoes, there are multiple styles you can choose from. Just go to your local drug store and see what they have. You can do full foot, heel only, arch only, etc.
Soaking the boot is a method used to stretch a boot that’s too tight. You soak the boot and wear it until it dries on your foot.
It’s the wrong idea for a boot that’s already too large! As above extra insoles or even a thick sock will help. If the shaft is tight you could try those ankle height terry sports socks over your thin boot socks.
A full sole insert would work fine.
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I bought a pair of size 8 Tredstep tall boots that are quite a bit too large in the foot. I went and got a couple of full sole inserts and ended up putting both of them in the boots. Now they’re quite comfy. Agree that soaking them won’t do anything to help.
To echo what others have said, bathtub method won’t work for your issue. Unfortunately, I know from experience 
I agree, bathtub won’t shrink the foot bed or do much for already formed leather. You can get shoe insoles that you can combine with heel lifts - my tredstep tall boots came with a thin extra insole and a short little heel lift per boot, you may be able to find one’s specifically for riding boots on ebay?
Actually, water can be used to stretch or shrink leather. However, when its the foot area that is too roomy, it may not shrink in the intended direction, because the leather upper will shrink while the size of the sole is fixed. So I agree that insoles of some sort would be the best thing to try.
If there is still too much room with an insole in place, then take a hand towel (something that will just fit in the area your foot occupies), soak in hot water, wring it out and stuff in the boot. Leave it in there for about half an hour, remove and let dry. A hairdryer can be used to hasten the drying process, but be aware that heat also shrinks leather. 
How about a pair of knee-high socks as you would normally wear under the boot, and then on top of that a pair of ankle socks that would only affect the foot part?
This is what I did for my boots that were a little bit too big. Worked like a charm and keeps your feet warmer in the winter!
