if the slackbuild is from slackbuilds.org, you can set the temporary folder to the location you prefeer exporting the TMP variable to the script, like
Code:
TMP=/my/path ./my.SlackBuild
it could work also with no-slackbuilds.org slackbuilds, just look at the top of it if the TMP variable is used, you should find something like
Code:
TMP=${TMP:-/tmp/SBo}
this means, "if not already set, give TMP the value of /tmp/SBo".
usually, the slackbuild scripts uncompress and build sources in $TMP/$PRGNAM-$VERSION and package them in $TMP/package-$PRGNAM.