This project is based on the Instructables "Hack a Toaster Oven for Reflow
Soldering" by frank26080115 at
https://www.instructables.com/id/Hack-a-Toaster-Oven-for-Reflow-Soldering/

Notable differences:

1) It uses an ArduinoUno as the processing element and all of the electronics 
(except the display, pushbuttons, buzzer, and relay) are mounted on an 
Adafruit Proto Shield -- all of the components are through-hole components.

There is a KiCAD project here. It includes a "four layer" board. Actually I
have no intention of creating a "four layer" PCB. I intend to build this on an
Adafruit protoshield (Product #2077). The PCB I "designed" with KiCAD is a
mock up for the Adafruit protoshield (almost). The red and green layers
represent the wiring already on the protoshield, and includes the bus strips.
The blue and white "layers" represent the added wiring. The board also
provides the approximate component placement. For those people without KiCAD
installed, I have included a PDF of the schematic in the file
ReflowToasterOven.pdf and some "pictures" of the board in the BoardPictures
folder (one is a screen shot of the KiCAD PCB layout and the others are from
the 3D viewer).

2) Everything is mounted in a pair of plastic boxes and instead of "hacking"
an extension code, an AC power entry module and a pair of AC Receptacles are
used.

There are three files related to the mechanical construction:

ReflowToasterOven-mech.tcl
ReflowToasterOven-mech.gcad
ReflowToasterOven-mech.dxf

ReflowToasterOven-mech.tcl is a Tcl program that generates the 
ReflowToasterOven-mech.gcad file, which is the input for the GCAD3D program.  
The ReflowToasterOven-mech.dxf is a DXF file, that can be imported to any 3D 
cad program.


3) An Adafruit 1.8" *Color* TFT LCD SPI display is used, using Adafruit's 
graphics library.

4) The software is a "standard" Arduino project.

And the code lives in the ReflowToasterOven subdirectory. It compiles
successfully and just fits in the Uno's flash memory and only 1/2 of the SRAM
is used by static variables, leaving just under 1K for dynamic variables.

You will need to install the Adafruit ST7735 and Adafruit_GFX libraries from 
Adafruit's GitHub repo.  You will also need the MsTimer2 library 
(http://www.pjrc.com/teensy/td_libs_MsTimer2.html).

*Most* of the code is copied from the original program by frank26080115.  I 
modified things to use C++ classes and adapted to use the Arduino I/O 
libraries, the Adafruit ST7735-based TFT display and the MsTimer2 library.

I have not built or tested it yet.