Arcan from the beginning has had good FreeBSD support. This is a guide for installing it on your FreeBSD system and additional tips for getting it configured for graphical acceleration without utilizing Xorg/X11. For the most part the build instructions just work as described on the project page and Wiki for Arcan.
The first thing which needs to be considered is setting up a FreeBSD system with compatible hardware. The main site makes reference to i965 Intel and Nvidia graphics drivers being the main ones tested. AMD GPUs theoretically should work but there are no promises in that regard, your mileage may vary. The machine I have used in this case has the following specs relevant to running Arcan is a [Dell Optiplex 990](http://i.dell.com/sites/doccontent/shared-content/data-sheets/en/Documents/optiplex-9