Some members often confuse skins with textures.
Skins, as you mentioned refer to the GUI (Graphical User Interface) or Hal's Window whereas textures are the various skin tones, clothing, scars, etc., that can be applied to a Haptek character.
I learned to create skins by examining a few simple skins of other designers. One needs to have a graphics program that will show the cursor's position in numeric form. In other words, the far left of the design box is 0, the far right might be 300 and so on. PSP or PhotoShop can do this as can several other programs.
A calculator will also come in handy for subtracting the cursor location for placement of your button or other objects.
Yes, you can position the various buttons anywhere on the skin design that you wish.
One of my skins was for a tall, full view character and should still be available here. Open the file and scroll through the various settings, etc., or open any existing ones in your Hal directory.
Hope this helps a bit.