First of all, you need to build libv4al which is available from Slackbuilds. Once you have built the package, make a new file under /usr/bin (or anyplace you like). Let's call it webcamSkype (or whatever suits you) and paste this
On my system, i put Skype under /opt/skype, so when you place Skype on different directory, you should change the path according to your system. Don't forget to make the script executable by running:
chmod +x /usr/bin/webcamSkype
Next, edit your shortcut using menu editor (assuming you are using KDE) and change the path to Skype binary into /usr/bin/webcamSkype.
If you want to make sure the webcam works, just use Options > Video Devices and click on the test button on the right top of the window. If it works, you can start video call using Skype with your friends, relatives, and colleagues