To make your turtle, start by printing out a copy of the sea turtle PDF below (it's a pdf version of this public domain sea turtle drawing)
If you would prefer to personalize your turtle, many other templates are available online under the search term "sea turtle outline".
Or, use the pdf as a template, and draw your own turtle friend!
Find a piece of scrap cardboard roughly the same size as your turtle.
Apply glue to both the back of the paper and the cardboard.
Place paper on cardboard and smooth out any air bubbles with another piece of scrap cardboard.
Wait 5-10 minutes for the glue to dry, then cut around the outline using scissors or knife.
Remove the flippers from the body by carefully cutting them away using scissors or a knife.
These will get attached to motors and power the turtle forward.