This is the sort of thing I use for keeping box turtles outdoors. This was for juvenile three toed but the Ornates are similar. The water on the left is only a couple of inches deep.
For Ornates there are a couple of things that I feel are really important.
Substrate depth. This has to be deep. At least twice their total body length. They like to burrow to avoid temperature extremes and also at night.
Ensure that the substrate doesnt get too wet, definetely not waterlogged. Perhaps cover a percentage of the enclosure with polycarbonate sheet or similar to maintain a drier area. They cannot handle wet UK conditions when its cool or cold. They get sick very quickly, even perfectly healthy animals can develop respiratory infections in days.
In the UK I wont put them outside until I can guarentee the weather is going to be dry and warm for extended periods. The deep substrate retains some moisture so they get the choice of microclimtes they need.Obviously they also need sunny spots as they are avid baskers.
The habitats I use for them oudoors are similar to the tortoise ones, except the plants have a chance to take hold without being eaten away which the turtles also utilise for shade and cover. In the wild this cover would be provided by long grasses so you could include those in your set up.
They are brilliant little turtles, very intelligent and bold. Make sure your outdoor enclosure is secure. A mesh top is a must for me as they are superb climers.