We’ve just published an article about a 3D printed jig to program some ESP8266 light bulbs, but as I watched Andreas Spiess’s latest video about ESP32 boards, he showed a board specifically designed to flash firmware to ESP-WROOM-32 or/and ESP-32S modules, which could be useful if you have many to program.
The acrylic base does not appear to be offered by all vendors, as some use some standoffs instead to lift the board up. You just need to insert your compatible ESP32 module in the board, flash the firmware it, take it out, and more to the next module. It can also be used as a development board since it exposes I/Os via three 14-pin headers, comes with a on/off button, reset and program buttons, as well as a micro USB port for power, programming and debugging
I first found it on Banggood, where it is sold for $14.99 shipped, the best price at the time of writing, but you can also purchase it on Amazon, eBay, Aliexpress, and I’m sure other websites. Just search for “ESP32 Test Board Small Batch Burn Fixture”.