Creating a Tinkers Construct/Tetra style mod using MCreator

How do I make the weapon creation system?

Hello! I'm interested in creating a mod similar to Tinkers Construct or Tetra, but I have no idea how to create the weapon creation system, as I am fairly new to GUIs and haven't made any working ones currently. If someone could help with this topic that would be great, but throwing ideas around for mods similar to this would be great as well.