Wash the oranges really well because we are keeping the skin on. Then slice very finely. I used a mandolin which makes easy work of this
If you have a food dehydrator, use according to your machines guidelines. I dried mine for approx a day and a half but this really depends on how juicy your oranges are and the thickness of the slices
If using the oven, preheat oven to 160 degrees C, pat oranges with a paper towel to absorb some of the moisture and then lay oranges on a fine wire rack. (something like a cake cooling rack would do). Bake for approximately 20-30 minutes checking often. Like above this really depends on the thickness of the slices so check regularly
For the chocolate
Break the chocolate up and add to a saucepan or metal bowl. Sit this over another saucepan with water in it to create a double boiler. Heat on the stove top until the chocolate has melted. Remove from the heat and dip the orange slices in to the chocolate and place on baking paper to set (takes about 20 minutes)
My oven instruction is a quick technique that I experimented with, but you don't quite achieve the results you do in the dehydrator. A quick search of the web and there are longer techniques that involve drying in the oven over 8 hrs.