How to go from dev board to custom PCB?

[JasperJoran]

I have a prototype design for a device that uses an Lolin 32 and accelerometer and a few other components. I would like to turn this into a custom PCB design to make the device more compact and more reliable. How should I go about doing this? The process of getting a custom PCB printed is relatively expensive so I don't want to make too many mistakes in the design. Are there any guides out there to doing this?

[ESP_Sprite]

The process of getting a custom PCB printed is relatively expensive...

Errm... no? Ordering custom PCBs has never been cheaper; you can get 5 medium-quality double-sided PCBs for a tenner or so, depending on size.

I'd advice you to pick a PCB program (I'm partial to Kicad, but there are lots of others like easyEDA, gEDA, DIPTrace, Altium, ...) and look up a tutorial or two for them; that should teach you the basics at least.