Generate a full detail guide on raised bed gardening. The guide should be a complete resource from construction to planting. It must include: 1. A detailed list of the benefits of gardening in raised beds (e.g., better soil control, fewer weeds). 2. A simple, step-by-step plan for building a 4x8 foot raised bed. 3. A guide to the best soil mixture recipe for filling your new bed (e.g., the 'lasagna' method). 4. A sample planting plan for a raised bed to maximize space. Please include a disclaimer about using pressure-treated wood.