• there is nothing special, I build 6 prototypes, with hand soldering, without issues

I am not saying best, they are just my steps :

• Solder CPU, and all active/passive components
• Burn bootloader> Connecting Atmel SAM-ICE> Chose Arduino zero native USB> Burn bootloader
• Solder Display
• Try some demo/test software
• Solder radio RFM95 module
• Solder buttons

• Download code, libraries, Burn.

  #include <Keypad.h>
  #include <RTCZero.h>
  #include <Adafruit_GFX.h>    // Core graphics library
  #include <Adafruit_ST7735.h> // Hardware-specific library for ST7735
  #include <SPI.h>              // include libraries
  #include <LoRa.h> //https://github.com/sandeepmistry/arduino-LoRa
  #include <FlashAsEEPROM.h>