I am not sure I can help you, but I will try to give advise in order that you can solve the problem yourself.
You are probably missing a module, try to find the module or kernel or whatever configuration which make unbuntu works.
After that, if the standard slackware kernel do not support your keyboard; you will have to find an alternative way to install Slackware. One way would would be to try to regenerate the Slackware CD with support for the keyboard (the procedure to regenerate the Slackware CD is documented in the isolinux/README.TXT directory of Slackware).
Perhaps an esier way is to install Slackware from Ubuntu (or whatever Linux which works). You only need installpkg and tar-1.13 (the 1.13 version of the tar program), renamed tar-1.13, you can find these utility from the pkgtools-11.0.0-i486-4 and tar-1.15.1-i486-2 Slackware package (extract these package with tar -zxvf on Ubuntu and place these utilities in your PATH). To install format a new partition, mount it on say /mnt/Slackware and issue the following command
installpkg -root /mnt/Slackware /path/to/the/slackware-directory/*/*.tgz.
Then configure your Slackware installation from ubuntu to support your kernel, write a proper /etc/lilo.conf in /mnt/Slackware and install lilo by lilo -r /mnt/Slackware