Breaking in a new custom glove doesn't have to be daunting. There are general steps you can go through to break in your glove.
Using warm water will help stretch the leather out.
Get a spray bottle with warm water and be generous with each area you're trying to work in.
I would start with a nice amount in the pocket.
Then hold the glove firmly on the outside—one hand on the pinky side and the other hand on the thumb side.
Face the pocket of the glove away from you and start to shear the glove up and down as if you were going to pull one hand down and the other up.
This motion will help soften the heel pad just below the pocket to form the necessary creases around the heel to start the crease up the thumb and the small crease on the palm.
Doing it this way will make it hard for any bubble or crease to form in the pocket.
Once the leather has been loosened up, using either a small wooden mallet or just a bat, we can repeatedly hit it into the pocket to help mold the pocket we want.
Sticking the hand in the glove during this process can help get a feel of where you want to catch the ball.
Each ball should be caught at the top of the pocket just under the webbing as an infielder.
So we start gently pounding there to get a good feel. If you are not pressed for time, and this is your backup glove (which, from a professional standpoint, is essential to own more than one glove), take some time to play catch with it and repeat from the beginning with warm water.
Note that water won't hurt the leather; it's a good tool in helping the glove take its shape.
The objective of the glove is to have the pinky and thumb of the glove to have maintained its stiffness while the creases in the heel of the glove allow the thumb and pinky to move.
This leaves a flawless pocket that is smooth and ready to catch without any annoying creases.
Conditioning the glove with glove oil will help keep the leather from drying out.
Don't over condition the glove and use a decent amount but wipe away any visible oil with a towel.
The method of keeping a ball in the glove and wrapping it up with a belt can be counterproductive if it's pulled too tight.
So make sure to notice any visible potential for a bubble or crease to appear.
Setting the glove down on the pinky and the thumb with the pocket facing the ground will also aid in keeping a crease form.