yuugake wo suru.

Because 釉掛け is being treated like an action noun.

The pattern is:

• X をする = to do X

So:

• 釉掛けをする = to do glaze application / to do the glazing

This is the same basic structure as:

• 勉強をする = to study
• 掃除をする = to clean

You can, and the nuance is slightly different.

• 釉を掛ける focuses more directly on the act of applying glaze to something.
• 釉掛けをする treats the whole thing as a named task or process.

So the difference is similar to:

• apply glaze vs.
• do the glazing

Both can be natural, depending on context.

Yes. 掛け is the noun/stem form of 掛ける.

In this sentence, 掛ける does not mean only to hang. It has a wider range of meanings, including to apply, to pour onto, to cover with, or to put onto something.

So 釉掛け is literally something like glaze-applying, which becomes the noun glazing or glaze application.

This is due to rendaku, the voicing that often happens in the second part of a compound word.

So:

• かけ → がけ

That is why 掛け is read as がけ here.

This kind of change is very common in Japanese compounds, although it does not happen in every single word.

Here, を marks 釉掛け as the thing being done by する.

So grammatically:

• 釉掛け = the activity
• を = marks that activity as the object of する
• する = do

Even though in English we do not usually say do glazing in exactly the same way, this is a very normal Japanese pattern.

Japanese often leaves out information that is clear from context.

So 釉掛けをする。 can stand alone if everyone already knows:

• who is doing it
• what item is being glazed
• when or why it is happening

In English, you often need to say more. In Japanese, context does a lot of that work.

They are closely related, but 釉薬 is the fuller and more common word for glaze. 釉 is a shorter, more technical-looking form.

So:

• 釉薬 = glaze
• 釉 = glaze, but in a more compact or specialized form

That is why 釉掛け sounds like a technical or craft-process term.

It is plain non-past style.

Some related forms are:

• 釉掛けをする。 = plain
• 釉掛けをします。 = polite
• 釉掛けをした。 = plain past
• 釉掛けをしない。 = plain negative
• 釉掛けをしている。 = is doing glazing / is in the process of glazing

No. The spaces are only there to make it easier for learners to read.

Normally, this would be written as:

• 釉掛けをする。

Japanese usually does not put spaces between words in ordinary writing.