If you have basic hand tools like a saw and a hammer you can build a simple, functional raised garden bed out of common lumber found at your hardware store. Modern treated lumber is safe for garden use, unlike in the past, and is weather resistant. This will keep out turtles and slow down weeds from overtaking your plants.
Purchase the following materials:
(6) 2"x6"x8' pressure treated boards
(1) 4"x4"x8' pressure treated post
nails or screws (at least 2-3" and rated for outdoor use)
garden soil or top soil with amendments of your choice
Cut two of the boards in half to make four 4' lengths. Cut the post into four 2' lengths.
Using the posts in the four corners, nail or screw the boards to the posts so that there are 2 boards on each side.
Dig 4 holes where the posts will go and put the bed in place. Backfill any holes with dirt.