Explain how we might keep a gas at a constant temperature during a thermodynamic process.

In accordance to ideal gas equation,
PV = nRT
Where P is the pressure of the gas, V is the volume of the gas, n is the number of moles, R is the gas constant and T is the temperature of the gas.
In the gas expands or contracts at constant temperature, the above ideal gas law (PV = nRT), is
PV = constant
The above equation (PV = constant) signifies that, keeping a gas at constant temperature the pressure of the gas will be inversely proportional to the volume of the gas.
Therefore in any thermodynamic process if a system is allowed to evolve such that the pressure of the gas is inversely proportional to the volume, then the thermodynamic process will bring no change in temperature.