Až bude večeře hotová, dáme talíře na stůl a zavřeme troubu.

Až is used for a future point: when, once, or as soon as something happens later.

In this sentence, Až bude večeře hotová means something like When the dinner is ready or Once dinner is ready.

A very common learner mistake is to use když everywhere for when, but až is the more natural choice here because this is a single future event.

Czech does not follow the same rule as English here.

After až, Czech normally uses the future when the event is really in the future, so až bude is completely normal.

So:

• Až bude večeře hotová = When dinner is ready / will be ready
• literally it contains a future form, but in English we usually translate it with the present after when

This is one of those places where Czech and English structure the sentence differently.

Because hotová has to agree with večeře.

Večeře is:

• feminine
• singular

So the adjective must also be:

• feminine
• singular

That gives hotová.

Compare:

• hotový oběd = a ready lunch
• hotová večeře = a ready dinner
• hotové jídlo = ready food

Here hotová is part of the predicate, not just a normal adjective inside a noun phrase.

The structure is:

• večeře = the subject
• bude hotová = will be ready

So večeře hotová means dinner ready as part of will be ready.

If you say hotová večeře, that is a noun phrase meaning ready dinner. For example:

• Hotová večeře je na stole. = The ready dinner is on the table.

In your sentence, the meaning is predicative: the dinner will be ready, so večeře hotová is the natural pattern.

Because they are perfective verbs.

In Czech, the present form of a perfective verb usually refers to the future:

• dáme = we will put / we will give
• zavřeme = we will close

But být works differently, so its future is built with bude, budu, budeme, etc.

So in this sentence:

• bude = future of být
• dáme = future meaning from a perfective present form
• zavřeme = future meaning from a perfective present form

This is very important in Czech grammar.

Literally, dát often means to give, but in many everyday sentences it also means to put, to place, or to set something somewhere.

So:

• dát něco na stůl = to put something on the table
• dát talíře na stůl = to put/set the plates on the table

This is completely normal Czech usage.

Here talíře is in the accusative plural because it is the direct object of dáme.

We are doing something to the plates:

• dáme talíře = we will put the plates

For masculine inanimate nouns like talíř, the accusative plural is the same as the nominative plural:

• nominative plural: talíře
• accusative plural: talíře

So the form does not change, even though the case does.

Because na can take different cases depending on meaning.

• na + accusative = movement toward a place
• na + locative = location at a place

Here there is movement:

• dáme talíře na stůl = we will put the plates onto the table

Compare:

• Talíře jsou na stole. = The plates are on the table
  Here there is no movement, just location, so Czech uses the locative: na stole.

Because trouba is the direct object of zavřeme, so it must be in the accusative singular.

The basic form is:

• trouba = oven

Accusative singular:

• troubu

This is normal for many feminine nouns ending in -a:

• žena → ženu
• kniha → knihu
• trouba → troubu

Because the sentence begins with a subordinate clause:

• Až bude večeře hotová = subordinate clause
• dáme talíře na stůl a zavřeme troubu = main clause

In Czech, a subordinate clause is separated by a comma from the main clause.

So the comma is required.

Sometimes you may hear it, and people would understand it, but až is the more natural choice here.

A useful rough distinction is:

• až = when/once for a specific future event
• když = when in general, repeated situations, or often past/present contexts

So for Once dinner is ready, we’ll..., až is the best fit.

Because Czech has no articles like a and the.

Whether something is definite or indefinite is usually understood from context.

So:

• večeře can mean dinner, the dinner
• talíře can mean plates, the plates
• stůl can mean a table, the table

If Czech really wants to make something more explicit, it can use words like ten, but often that is unnecessary.

Because Czech often leaves out subject pronouns when they are clear from the verb ending.

Here:

• dáme = we will put
• zavřeme = we will close

The ending -me already tells you the subject is we.

You could add my for emphasis or contrast:

• My dáme talíře na stůl. = We will put the plates on the table.

But in a neutral sentence, Czech usually omits it.