Here is the fully assembled thermometer.

Slide the battery compartment cover off by applying downward and forward pressure.

Loosen and remove the four screws from the back of the thermometer.

Lift the back panel away from the rest of the case.

Remove the three screws holding the circuit board in place.

Lift the circuit board away from the case.

Remove the screen from its compartment.

Remove the push buttons from their compartment.

Here's a full view of the disassembled components (circuit board, screen, push buttons, and case).