How to design for electrical connection for a food dryer
I would suggest the easiest way of doing this is to modify a cheap oven, if you very crudely turn on and off an oven based on a temperature sensor inside you can get pretty accurate results.

By using a standard oven you do not have to worry about the heating element or the even distribution of heat since this is most likely already taken care off by the manufacturer of the oven.

The easiest way of doing this, is getting a relay, PID controller(or arduino with PID loop), a suitable temperature sensor(maybe a thermocouple) and connect them together. There are several tutorials of people making these products search for "PID Arduino oven" or anything similiar.
Here are some results Result 1, Result 2.

The most important part of the build is the PID loop, You set the temperature you want to reach or a curve you want the temperature to follow. The relay will be connected to the mains and turn the oven on and off to reach this temperature. The feedback loop will be the thermocouple sensor, reporting back the temperature to the Arduino or PID controller.