This is a simple two part case for a ESP8266 USB programmer I designed. The programmer works with the Arduino IDE to program the target board in the same way the Wemos and Node MCU development boards work. The idea here is that the target board would only need a 6 pin header for external programmer to plug into, no need for the USB circuit on the target. This is both cheaper and simpler to make it's also great for low power ESP8266 designs, as you are not powering the programmer circuit once it is unplugged.

I have more info at https://www.mottramlabs.com/products.html also a few boards https://www.ebay.co.uk/sch/mlabs2018/m.html?_nkw=&_armrs=1&_ipg=&_from=