My husband made the beds about 10 years ago from boards of 2×6 pressure treated lumber (oops! Don’t use pressure treated lumber for your gardens, although the newer types may be safe. I’ll add a link soon about the hazards of this in gardens). They measure 3.8 ft by 9 ft. I have five adjacent beds. Between each is a pathway that ranges from 15 to 17 inches wide, but you might want to make them wide enough for your rake (I use an adjustable rake).
To make the beds, my husband just laid the wood on the surface of ground. He made stakes (about 2x2x12) that were pounded into 3 of the 4 corners of each bed. The frame is screwed into these stakes. The stakes hold the beds in place.
After making the frames, we filled them with about 3 or 4 inches of a mixture of peat, composted manure and topsoil. All were purchased in bags. I turned this mixture to mix it with the soil below. As I remember, it took me a few years to get the beds full to the top – they hold a lot of soil.
I have a nice composting system where I compost most of my garden waste. Every year a good amount of this goes into the beds and is turned under along with the cover crop that I’ve planted for the winter.
The raised beds work great and look nice. Well, most of the year they look nice – right now they are quite a mess….