This HOWTO explains how to compile GRASS GIS on Slackware.

su - # switch to root
 
# create postgres group and user for postgresql, one of pdal dependencies
groupadd -g 209 postgres
useradd -u 209 -g 209 -d /var/lib/pgsql postgres
 
# install dependency libraries;
# build queuefiles, not packages, to automatically build any other dependencies
sbopkg -k -i "proj gdal pdal"