1. Have enough resources to create at least 1 of whatever item you want to make.
2. Save before attempting the glitch just in case you mess up and actually use your resources.
3. Find and hover over the item you want to create in whatever workbench or station it's within.
4. For Xbox, press "A" and then quickly after "B". For Playstation, press "X" and then quickly after "O".
5. If you did it fast enough then you will have a confirmation box on your screen showing you exactly how many resources that item costs to create and asking you if you're sure you want to create it. In the background behind it you will also notice that you went to the previous menu that comes before where your item is shown.
For example, on the chem station for stimpaks, the menus go "Categories" > "Healing" and then you will see stimpaks along with other items you can create that heal you. If you do the glitch correctly it will take you back to the "Categories" menu as well as still have a confirmation screen pop up asking you if you want to create the stimpak.
6. Assuming you did the glitch correctly and have the confirmation screen, choose to create your item.
7. Rinse and repeat as much as you want and with any items you can create on a workbench or station.

*Note* If you do this glitch with mods on armor or weapons, you need to do it twice in order for the mods to be equipped.
For example, if you want to put a recon scope on your sniper you would hover over that mod, do the glitch which will create the mod, but then you need to go back and hover over it and do the glitch a second time to actually equip it to the gun.

If you have any questions or need any help just let me know.