hackaBLE is a tiny (~ 18 mm x 28 mm) Open Source Nordic nRF52832 based BLE development board you can embed in your BLE projects. It’s designed such that you can use it in three ways:

On a breadboard
On a custom PCB, hand-soldered easily using the castellated 2.54 mm pitch headers
On a custom PCB, using a stencil and oven, making use of extra pads underneath the PCB