RHS Research’s PicoEVB FPGA dev board based on an Artix-7 A50T FPGA snaps into an M.2 2230 key A or E slot, which is common in newer laptops. The board measures 22x30mm, which is slightly larger than the Artix-7 FPGA and configuration EEPROM mounted on one side of the board. It has a built-in JTAG connection that works natively with Vivado.
Here’s a photo that shows you the board’s size in relation to a US 25-cent piece:
Even though the board itself is small, you still get a lot of resources in the Artix-7 A50T FPGA including 52,160 logic cells, 120 DSP48 slices, and 2.7Mbits of BRAM.