I had this problem also. Alien Bob's wine slackbuild is following winehq spec on where to install the mono package, however this doesn't seem to be correct and wine can't find the mono library when launched so it attempts to download it. Changing the following lines in the wine.SlackBuild should fix the problem. It did for me.
change...
Code:
# Add the wine-mono MSI installer to the Wine package:
if [ "$MONO" != "NO" ]; then
mkdir -p $PKG/usr/share/wine/mono/wine-mono-${MONO}
install -m0644 ${MONOSRC} $PKG/usr/share/wine/mono/wine-mono-${MONO}/
fi
to...
Code:
# Add the wine-mono MSI installer to the Wine package:
if [ "$MONO" != "NO" ]; then
mkdir -p $PKG/usr/share/wine/mono/
install -m0644 ${MONOSRC} $PKG/usr/share/wine/mono/
fi