Apologies but here I share about the OpenBoard software I have been using for nearly two years now. http://www.openboard.ch/index.en.html It is developed by some folks in Switzerland. I am from rural southern Illinois and live in northwest Beijing. I use it with a Wacom Cintiq-13 tablet in lectures I give. I save my .ppt and .odp as .pdf which can be annotated in OpenBoard. Its display is compatible with OBS-Studio as a capturable window. One can capture live video from a camera and put that with the OpenBoard display for recording or sharing live online. It also is great for meetings and teaching. You do need a computer with at least 2 video ports, one for the display screen and one for the Wacom. More displays are useful for studio recording and remote conferencing.

There was a quite difficult method I used originally to install OpenBoard in Slackware at first. I have just found a rather simple method for Slackware64 -current that someone with actual skill could refine.
1. Install ffmpeg if you don't have it already and ffmpeg3-compat package from AlienBob repo.
2. Download the .deb from : https://github.com/OpenBoard-org/Ope....5.3_amd64.deb
3. Convert the .deb to tgz with deb2tgz and install with installpkg in the usual way.
4. The executable is located in /opt/openboard/OpenBoard
That was all it took for me. Some deps may have been gathered in process of other things I am using, but this is a recent clean install of 64-current kept up-to-date.

Thanks for the heads-up on this.

I would like to try the openboard slackbuild, but I will need some guidance. I have managed to copy the slackbuild files to my computer, but cannot see how to get the correct openboard source.

see the openboard.info

Since I stumbled upon this link to willy's slackbuild I continued to use openboard in my everyday work and I think it's perfect for videoconferences and also for face-to-face lessons. Any plan to add it to ponce's slackbuilds repo? Or the repo is only for packages that are already in slackbuilds.org?

ponce's repo is to track changes needed for -current system