Stavi podmetač ispod vruće tave.

Stavi is the 2nd person singular imperative of staviti.

So it means put! / place! when you are telling one person to do it.

• staviti = to put, to place
• stavi = put! (informal singular)
• stavite = put! (plural or polite/formal)

This is about aspect, which is very important in Croatian.

• staviti is perfective: one complete action
• stavljati is imperfective: repeated, ongoing, habitual action

So Stavi podmetač... means Put the mat there now, as one completed action.

If you said stavljaj, it would sound more like:

• keep putting it there
• put it repeatedly
• be in the process of putting it

For a simple one-time command, stavi is the normal choice.

Croatian often omits the subject pronoun, especially in commands.

The ending of stavi already tells you that the command is directed at you (singular, informal), so ti is not needed.

You could say Ti stavi podmetač..., but that would add emphasis, contrast, or impatience.

Podmetač is in the accusative singular because it is the direct object of the verb stavi.

You are putting what?
→ podmetač

For many masculine inanimate nouns in Croatian, the accusative singular looks the same as the nominative singular.

So:

• nominative: podmetač
• accusative: podmetač

Same form, different function.

Ispod means under / below / underneath.

It introduces the place where the object should go:
ispod vruće tave = under the hot pan

A key grammar point is that ispod takes the genitive case, which is why tava changes form.

Because ispod requires the genitive.

The noun is tava = pan, and its genitive singular form is tave.

So:

• nominative: tava
• genitive: tave

That is why you get ispod vruće tave.

The adjective must agree with the noun in gender, number, and case.

Here, tava is:

• feminine
• singular
• genitive (because of ispod)

So the adjective also has to be feminine singular genitive:

• vruće tave = of the hot pan / under the hot pan

Compare:

• vruća tava = hot pan (nominative)
• vruću tavu = hot pan (accusative)
• vruće tave = of the hot pan (genitive)

Yes, and in many situations that is very natural.

Croatian often uses:

• pod + accusative for movement to a position under something
• pod + instrumental for being located under something
• ispod + genitive for the space below/underneath something

So:

• Stavi podmetač pod vruću tavu. = Put the mat under the hot pan.
• Stavi podmetač ispod vruće tave. = Put the mat underneath the hot pan.

Both can work, but the structure is different:

• pod vruću tavu → accusative
• ispod vruće tave → genitive

Podmetač is something you place under another object to protect the surface.

Depending on context, it can mean things like:

• trivet
• mat
• coaster
• pad

In this sentence, because the pan is hot, trivet or heat-protective mat is the best idea.

Because Croatian has no articles.

So Croatian does not have separate words that directly match English a/an and the.

Whether podmetač means a mat or the mat, and whether tava means a pan or the pan, depends on context.

Yes. Croatian word order is fairly flexible because case endings show the grammatical relationships.

The given sentence is a normal, clear order:

• Stavi podmetač ispod vruće tave.

But you could also say:

• Ispod vruće tave stavi podmetač.

That version puts more emphasis on where the mat should go.

So the meaning stays basically the same, but the emphasis can shift.

Use stavite instead of stavi:

• Stavite podmetač ispod vruće tave.

This can mean:

• speaking to more than one person
• speaking politely/formally to one person