It's fairly easy to determine dependencies and source file locations if you just download the SLACKBUILDS.TXT file and use parsing tools to search through the "REQUIRES" and "DOWNLOAD_x86_64" fields in that file. You can find that here:
https://slackbuilds.org/slackbuilds/...LACKBUILDS.TXT
I use my own bash script that determines the dependency list from that file and then downloads each slackbuild file and sources into a numbered list of directories in the correct build order. Kind of like a helper script to ease looking through all the pages of deps on the actual site. There are other public tools out there that do the same thing too.
