DIY: How to Build Kitchen Sink Storage Trays - excellent instructions, plus lots of pics to show you how. No special tools required/beginner's project.
Build these handy undersink roll-out trays in a weekend. You can tackle this project with simple carpentry tools and some careful measuring. You can make all the trays in an afternoon using building products from your local home center or hardware store for as little as $80.
Also on these boards
window seat with storage below.
I would like one of these, it even has storage.
How to Build a Storage Ottoman | Step-by-Step | This Old House