س ط حs-ṭ-ḥ
(ف) سَطَحَ يَسْطَحُ سَطْحًاsaṭaḥa yasṭaḥu saṭḥan: to spread out; to make level and even. ﴿وَاِلَي الْاَرْضِ كَيْفَ سُطِحَتْ﴾ (Al-Ghāshiyah 88:20)
سَطْحٌsaṭḥ pl. سُطُوْحٌsuṭūḥ (noun, ism dhāt): a flat upper surface; a roof.
مِسْطَحٌmisṭaḥ (noun of instrument, ism ālah): a board on which things are spread out.Only once in the Quran, and that in the passive voice.