on Slackware

using SlackBuilds

SlackBuilds.org

ftp.slackbuilds.org user:anonymous empty password pub/slackbuilds/15.0/[category]/
print readme to stdout (dash as target file): get [name]/README -
the footer also lists a git repository url

.info files

wget -cv "`grep -oP '(?<=DOWNLOAD=")[^="]+' "${PWD##*/}".info`"

.SlackBuild

sudo sh "${PWD##*/}".SlackBuild #will do fine, no sbin usage
sudo /sbin/installpkg #however. just use su for quick PATH