In my previous build of reflow oven, I used very simple controller based on Atmega328. Here is picture of my board, which I designed for this purpose. 

Board was based on schematic of Reflow Oven Controller Shield (Arduino Compatible), but I wanted it like complete  board so I implemented MCU on it. It was not perfect, but it worked. On top of this board  was 16x2 LCD (JP1) and board from Adafruit with thermocoupler (MAX31855) was plugged to the SV2 header. SSR was hidden on side of the oven. Usaga was very easy, one button controlled start or stop of the heating profile. This was years back, when I just start playing with Arduino.  

This oven controller is based on very popular ESP32 controller and I build it to have this Basic features:

• TFT display 
• SD card
• SSR control
• piezo speaker
• IC which wiil read temperature from thermocoupler
• buttons for control & setup of the controller

In future I would like to also have Advanced features such as:

• menu with settings for profiles, SSID & password, etc.
• webserver for viewing reflow progress 
• reflow profile parsing from JSON (stored on SD card or in NVM of ESP32)
• saving logs from reflow process to SD/NVM

  When I was waiting for arrival of my oven, I designed this board in Autodek Eagle. 

I used ESP32 WROVER chip, as I also use them in other projects. Well known CH340G is used for programming & UART communication. For temperature reading I used MAX31856 because it can read multiple types of thermocoupler´s. TFT has ILI9341 driver.  

Board are in production, so I can look at what´s inside of oven :).