Below are some clips showing a female painted turtle (Chrysemys picta) build her nest and lay eggs.  Enjoy!

After coming on land and finding a suitable site, the female turtle excavates her nest, which is a flask shaped chamber in the ground.  In the video, you can see her digging, one foot first and then the other, removing mud one scoop at a time.  The female then lays her eggs (oviposits), gently positioning each egg in the nest after laying it.  Female painted turtles generally lay 8-12 eggs at a time.  Finally, the female closes her nest by moving soil back over the top of the nest opening, and stomping it down to form a solid plug.  The entire process takes about an hour (each video is just a short clip), after which the female will return to the water.  Eggs are laid in May and June, and generally take three months to hatch.  At the Janzen Laboratory's research site in Illinois, the hatchling turtles remain in their nest through winter, finally emerging the following spring.  

Female painted turtle excavating the nest