What are the best methods to stretch new tall boots?

Initially, try to wear them before a competition. The leather will be made to your leg and so will soften.
You can also help them with a jar of milk or cream for the leather (you can buy them everywhere), it will nourish the leather and allow it to soften if your boots are new or they haven't been worn for a long time.

Then for the maintenance of your boot I advise you to pass a soft blow of brush to remove the sand and the probable projections of mud (it will avoid that your leather is damaged and does harden) after each use. Clean them thoroughly with a damp sponge. Be careful, avoid using glycerine soap ... Indeed, it will soften your boot but far too much. Glycerin soap is made for bridle leather. If you put too much, your boot will slip on your leg (like a sock) and the elastic of your boot (if any) will completely relax. Believe me, I made the mistake of doing this and my boots no longer hold ...

Also if your boots are very wet (due to rain or other), fill the paper with newspaper and allow the paper to absorb moisture. Do not put them against a radiator, the leather of your boots may harden.

A little shake: and HOP! your boots will be beautiful and comfortable
I meant Mink Oil* it will stretch supple and soften the boot leather. water may dry it out - i would never dunk any of my $400 tall boots into a bucket of water tbh but in warmer areas i could see how thatd be the preferred method hahha
Douse them in milk oil and wear em
I agree with Joel, while wearing them step into a water trough and then wear them the rest of the day. It sucks but it breaks them in in just one day
Just wear them around the house 😄
Get them soaking wet (very uncomfortable) and wear them all day working and riding in the barn.
I was told to spray the inside with rubbing alcohol and then put them on and wear them around
Oil them after standing in water for like 30 seconds or sleep in them
Put a heel lift in until they drop. Wear them while you bathe horses...not helpful this time of year lol
My trainer has always told me to stand at the edge of a stair and hang my heels as far down as i can.