Ik zat gisteren laat te werken, maar om elf uur ben ik toch onder de deken gaan liggen.

Zat te werken gives an ongoing, in-progress feeling: the speaker was in the middle of working. It also literally suggests a seated posture, which fits desk work well.

So:

• Ik werkte gisteren laat = I worked late yesterday
• Ik zat gisteren laat te werken = I was sitting there, working late yesterday / I was working late yesterday

The second version is a bit more vivid and scene-setting.

After verbs like zitten, staan, lopen, and sometimes liggen, Dutch often uses:

posture verb + te + infinitive

So:

• zitten te werken
• staan te praten
• lopen te zoeken

This construction often means someone is busy doing something, often with an implied physical posture or movement.

Yes. That sentence is completely correct.

The difference is mostly one of nuance:

• Ik werkte gisteren laat = simple statement of fact
• Ik zat gisteren laat te werken = paints the situation more clearly, as something ongoing

So the original sentence sounds a little more natural if the speaker is describing what was happening at that moment.

Both are possible, but they are not identical in feel.

• ging ik ... liggen = simple past, often more narrative
• ben ik ... gaan liggen = perfect tense, very common in spoken Dutch when talking about a completed action in the past

Unlike English, Dutch can use the perfect tense quite naturally even with a specific past time such as om elf uur.

So om elf uur ben ik toch onder de deken gaan liggen is very normal Dutch.

Dutch uses zijn as the auxiliary with many verbs of:

• movement
• change of state
• becoming / beginning a new position

Gaan liggen means to go lie down / to lie down, so it involves movement into a new position. That is why the perfect uses zijn:

• Ik ben gaan liggen
• not Ik heb gaan liggen

This is similar to other verbs like:

• Ik ben gegaan
• Ik ben opgestaan
• Ik ben gevallen

Because liggen means to be lying, while gaan liggen means to lie down or to go and lie down.

So:

• Ik lig onder de deken = I am lying under the blanket
• Ik ga onder de deken liggen = I am going to lie down under the blanket
• Ik ben onder de deken gaan liggen = I went and lay down under the blanket

The original sentence is about the moment the speaker changed position, so gaan liggen is the right choice.

This is a classic Dutch pattern called IPP (Infinitivus Pro Participio).

With certain verbs, especially when one infinitive depends on another, Dutch often uses an infinitive where you might expect a past participle.

So standard Dutch says:

• Ik ben gaan liggen
• Ik heb het zien gebeuren
• Ik ben blijven zitten

rather than:

• Ik ben gegaan liggen
• Ik heb het gezien gebeuren
• Ik ben gebleven zitten

For learners, the easiest rule is: with verbs like gaan, blijven, laten, zien, horen, etc. followed by another verb, Dutch often keeps that first verb in the infinitive in the perfect tense.

Toch is one of those small Dutch words with lots of nuance. Here it means something like:

• still
• after all
• anyway
• nevertheless

In this sentence, it suggests a contrast such as:

• even though I was working late, I still went to bed at eleven
• maybe I had been continuing for a while, but I did go lie down in the end

So toch adds the feeling of despite that, in the end.

Dutch main clauses follow the V2 rule: the finite verb must be in the second position.

In the second clause, om elf uur comes first. That means the finite verb ben must come next:

• Maar om elf uur ben ik toch onder de deken gaan liggen.

So the order is:

1. om elf uur
2. ben
3. ik
4. the rest

If ik came first, you would get:

• Maar ik ben om elf uur toch onder de deken gaan liggen.

That is also correct. The difference is just which element is being foregrounded.

Both are possible, but onder de deken sounds more natural if the speaker means the blanket on the bed / the usual blanket in a known situation.

Dutch often uses the definite article when the thing is understood from context.

So:

• onder de deken = under the blanket, the one we naturally have in mind
• onder een deken = under a blanket, any blanket

In a bedtime context, de deken is the most natural choice.

Yes. Both can occur.

• onder de deken = under the blanket
• onder de dekens = under the covers / under the blankets

The plural dekens can sound a bit more like English the covers, while the singular focuses on one blanket. The sentence with de deken is perfectly natural.

Gisteren laat is the natural order here because gisteren sets the time frame and laat adds the detail that it was late.

So:

• gisteren laat = late yesterday / yesterday until late

Laat gisteren would usually suggest something more like later yesterday or late in the day yesterday, and it is not the best fit here.

So the original order is the idiomatic one for this meaning.