These toe kick plans (cabinet platform, toe base, cabinet base, etc.) are based on a design used by a cabinetmaker I worked with several years ago. I particularly like the use of a continuous front and rear stretcher. This provides a solid base for fastening to the platform at any point along the front or back of the cabinet.
The cross supports, placed every 18", are best notched at the bottom to accommodate uneven flooring. My preference is to level the toe kick, then fasten it to the wall and the floor before installing the base cabinets.
When the floor is perfectly flat and level, this isn't such a big deal. But floors are rarely perfect and it's much easier to level the base by itself than to wrestle an entire run of heavy cabinets.
Shim between the kick and the floor and the result will be a level, sound foundation on which to install your cabinets. Any gaps between the kick and the floor can be covered with wood baseboard, rubber cove base, plastic laminate, tile, or carpet.
Since you'll be covering it with some sort of base, nearly any 3/4" material can be used. However, for potentially wet areas (kitchens, bathrooms, garages, etc.) you should not use particle board. Plywood is a much better choice. If it will be regularly exposed to water, marine grade plywood is even better yet.
Note that the front is 1" longer than the back on each end. It's designed for a 30" wide cabinet installed between two walls that are 32" apart. A 1" scribe would be attached between the cabinet and the wall on each side.
The difference in length between the front and back forms two "ears" that can be trimmed to fit, if necessary. For cabinets installed against only one wall, leaving an "ear" on the wall end helps the kick fit neatly in a corner that is out of square.
Assemble with glue and nails or staples at every joint. Screws can be used but are not necessary for a strong, stable cabinet foundation.
To view the plans just click here. If you'd like to download a copy to your computer, right click then "save-as". Either way, you'll need the Adobe reader to view the file.