Here's a second 15.0 rootfs alpha build, 2.3 Go compressed:
https://slackware.openpandora.org/pandora/sl4p/sl4p-15.0/rootfs/
To install it, use a 32 Go or more SD card. Create a first EXT 2, 3 or 4 partition on it, and eventually a second partition with swap which will be used automatically...