FWIW , just heated to a gentle dryness, 35 ppt seawater will probably read very roughly 4 ppt too high due to hydrated magnesium chloride and sulfate.
There won't be much solids, but I wouldn't reuse it as the alkalinity will mostly be gone into calcium and magnesium carbonate, which won't redissolve.
If i do this at home on the oven what steps would i do? Will try it just to veryifiy that my refractometer is working correctly or in range.