Two-dot ice radical on the left - a graphic shorthand for frozen water, marking 冻 as a cold-related verb. Pairs with 冷 cold, 冰 ice, 凉 cool, 凝 to congeal. The left-side 冫 cleanly indexes the whole cold-and-freezing family in everyday Mandarin.
Right side 东 gives the sound - dōng shifts only in tone to dòng. The traditional 凍 used the unsimplified 東 in the same role. The east-direction meaning is incidental; 东 here is purely sound, paired with the ice radical to spell out 'freeze'.
