“Take a large tablet.” This announcement of the Assyrian invasion (of Syria, Israel, and then Judah) was to be public. The tablet, and the baby that was to be born, were to be signs to Judah (cp. Isa. 8:7). The Hebrew word for “tablet” is gillaovn (#01549 גִּלָּיוֹן), which generally refers to a tablet of wood or metal that would be capable of being put up as a placard to be read by many people, and that is likely the case here.
“stylus of a man.” This is most likely an idiomatic way of saying, “an ordinary stylus.” In other words, Isaiah was not to engrave the tablet with some special instrument. However, because the phrase is an idiom, different scholars have different ideas about the emphasis it is bringing to the text. For example, the ESV has, “write on it in common characters.” In that case, the stylus would be a metonymy for what the stylus wrote, but there does not seem to be any good reason for importing the metonymy into the verse.
“Maher-Shalal-Hash-Baz.” Biblical names, especially when they were given by God, were always descriptive of the person in some way; they were mini portraits of the person or some aspect of the person’s life. It is impossible to give an exact translation of a name for several reasons. First, it is not written as a sentence so the connectors have to be supplied. Secondly, the Hebrew words involved can often be translated differently. For example, in this name, the Hebrew form of the first word, maher, can either be an infinitive verb or an imperative verb, and the way those can be brought into English can differ. Thirdly, the words themselves have different definitions, but the translator has to choose one for his translation. This explains why different commentaries or study Bibles have somewhat different meanings for the name. The essence of the name is something like: “Haste to the spoil; hurry to the prey (or plunder),” or “speeding to the plunder; hurrying to the spoil.” In this case, the name foretold the conquests of the Assyrian Empire over Syria and Israel (Isa. 8:4), and even over much of Judah as well (Isa. 8:8).