I usually add an
Code:
export MAKEOPTS="-j4"
to /etc/sbopkg/sbopkg.conf: it should work with slackbuilds using make to compile, assuming they support parallel builds.
in rare cases they don't, but in these situations you can pass as an extra parameter for those slackbuilds (in the queue or the command line, using the syntax specified in the man page) the MAKEOPTS="-j1" variable that should override the one in sbopkg.conf.