To find cloud base = (Surface Temp - Dewpoint) X 1000feet and divide the answer by the dry adiabatic lape rate (DARL 3 deg. celcius/1000').
Exemple: SFC temp 15c, DP 9c.
(15-9) X 1000= 6000feet divided by 3 = 2000 feet
Cloud base at 2000 feet.
To find FZ LVL; dewpoint divided by saturated adiabatic lapse rate (SARL 1.5 deg. c/1000') multiplied by 1000. Then add cloud base and you have your freezing level.
(DP/SARL) X 1000 and add cloud base to answer.
Exemple: (9/1.5) X 1000= 6000 + 2000= 8000 feet
Freezing level @ 8000 feet.
Cheers