en_tn_condensed/2ch/06/12.md

in the presence of all the assembly of Israel

"in front of the people of Israel who had gathered there"

spread out his hands

"raised his hands." This was to show that he was praying. (See: rc://en/ta/man/translate/translate-symaction)

five cubits long, five cubits wide, and three cubits high

You may convert these to modern measures. AT: "two and one-third meters long, two and one-third meters wide, and one and one-half meters high" (See: rc://en/ta/man/translate/translate-bdistance)

he spread out his hands toward the heavens

Solomon lifted up his hands and held them high as he knelt on the platform to pray. Spreading out his hands toward the heavens was a way of showing that he was praying to Yahweh. (See: rc://en/ta/man/translate/translate-symaction)