SlackBuildsOrg/system/mongodb

MongoDB is a scalable, high-performance, open source document-oriented
database.

You'll need to create a mongo user and group in order to run mongo with
the provided init script:

# groupadd -g 285 mongo
# useradd -u 285 -d /var/lib/mongodb -s /bin/false -g mongo mongo

You'll also need to add the following to /etc/rc.d/rc.local

if [ -x /etc/rc.d/rc.mongodb ]; then
    /etc/rc.d/rc.mongodb start
fi

NOTE: This script repackage binary source