Any advice on creating a raised garden bed?
Well, depends. Lazy me - I have put down cardboard over the yucky area. Stacked concrete blocks around it. Dumped Compost, Vermiculite, and Peat Moss in equal volumes mixed well. Plant and water. I just use a yard stick to measure rather than a grid.
https://www.amazon.com/dp/B00CN1W1RO/#customerReviews
Low Maintenance Raised Bed Gardening Book free-for a very short time-kindle book