The 2x2x3 Large Slim Tower aka "Franken Tower" is a cube type transformation using a standard 3x3x3 57mm Rubik's Cube and two super 57mm 2x2x2 Cubes. The raw materials to make the Franken Tower are purchased directly from rubiks.com. The Franken Tower's dimensions are 57mm x 57mm x 86mm. See the above image for a direct comparison between a standard Slim Tower, a Rubik's Cube, and the Franken Tower.
The general principle for making a standard Slim Tower is explained in the Tony Fisher's Cuboid 3x3x3 Transformations section of twistypuzzles.com. A useful tutorial for creating one can be found at Ton Dennenbroek's excellent web page.
Given that a standard Rubik's Cube is 57mm across and the Super Pocket Cube is also 57mm across, the internal mechanism of the Rubik's Cube requires significant modification beyond what is necessary for a standard Slim Tower. While using a smaller 3x3x3 cube would be expedient for creating the Fraken Tower, one cannot be assured of the consistency and quality of knock-off cubes which would have to be used if smaller than the standard 57mm size. Therefore it was best to stick to a known quality product and to develop a standardized creation method around it. The end result is a puzzle that turns very smoothly and is suitable for some light/moderate speed cubing due to its rugged interior design and larger size.
Cost for a "Franken Tower" is $135. The price will include shipping worldwide. You may specify a sticker color pattern if you so choose. Otherwise it will get the standard official Rubik's Cube pattern as shown on this page.
So you wanna take your "Frankie" apart, do you? I don't recommend it. If you're curious, scroll down to the bottom for a pic of the disassembled prototype. If that's not enough for you and you really wanna peek inside... Well I can't cough up all my secrets easily, can I?
Some prototype Franken Tower pictures below.