To design an experiment measuring how magnetic field strength varies with temperature, a Hall probe can be used for measurements. The magnet can be submerged in a non-magnetic liquid, such as oil, which should have a density sufficient to suspend the magnet and ensure uniform temperature distribution. Heating the liquid allows the magnet to reach thermal equilibrium, requiring a stabilization period before taking measurements. After stabilization, the Hall probe can be positioned outside the container, and if the magnet is too far, a Pyrex stirrer rod can be used to gently move it closer for accurate readings. This method ensures consistent temperature and effective measurement of the magnetic field strength.