Warning, this project involves working with potentially lethal high voltage wiring, know what you are doing.

I went with a cheap toaster oven with quartz tubes on the top and bottom.

Heater rated power

1000W was sufficient due to the small volume of the oven.

Front panel

You may select an oven with similar front panel to avoid having to cut anything. The software is optimised for a round display. 

Automatic door mechanism

If you would like the automatic door mechanism, whether it can be easily done will vary between ovens. For my type of oven, the door is connected to the internal part of oven. Hence, it was easily to integrate without resorting to external mechanisms; outside of the oven's body.

PCB

Purchase the display pcb extension and receiver set if you're intending to use a similar display setup as mine.

Components

Purchase the components according to the bill of materials (Incomplete)

I printed 2 parts: 

A mount for the display to be glued (not optimised for the curvature of the oven)

A mount for the rotary encoder

Install the display and UI library. In addition, install my Audio library and other dependencies from Github.

Compile and flash firmware using Arduino IDE.

The optimal parameters greatly depend on your oven and location of the temperature sensor.

Congratulations, you have successfully built a reflow oven.