So I am assuming that every executable script located in the /etc/rc.d directory will be executed with the start statement when the slackware boots. Am I right?
The rc scripts that come with Slackware (like rc.mysqld, rc.alsa) are called from one of the other rc scripts. If you add your own rc file to /etc/rc.d/ you will have to add a couple of lines to rc.local that will start your program. Look in rc.M for inspiration. Generally it would look like this (example for an imaginary rc.ntp script):
# Set correct time and date, and start the ntp daemon:
if [ -x /etc/rc.d/rc.ntp ]; then
So, by making the script executable you will cause it to be started when the computer starts. The rc.local file will be run after all the other rc scripts have run.