Learn Hardcore Indonesian: Di laci kecil itu, ada selembar kertas untuk menulis nomor ojek. - In that small drawer, there is a sheet of paper to write the motorcycle taxi number.

Di laci kecil itu, ada selembar kertas... = In that small drawer, there is a sheet of paper...
For possession, use punya or memiliki (e.g., Saya punya buku = I have a book). Using ada to mean have (Saya ada buku) is colloquial/regional and not standard.

Why does the sentence start with Di laci kecil itu? Can I put the location at the end?

Starting with the location is common in Indonesian to set the scene or emphasize place.

Location first (emphasis on place): Di laci kecil itu, ada selembar kertas...
Location last (neutral, very common): Ada selembar kertas ... di laci kecil itu. Both are correct.

Do I need the comma after the initial location phrase?

It’s optional. Many writers include a comma after a fronted adverbial phrase, but short ones like this often appear without a comma. Both are acceptable.

Why is it laci kecil itu and not itu laci kecil?

Indonesian noun phrases typically go Noun + Adjective + Demonstrative.

laci kecil itu = that small drawer (noun phrase)
laci itu kecil = that drawer is small (full clause)
itu laci kecil is not how Indonesian forms that noun phrase.

What does itu add here?

Itu marks the drawer as specific/identifiable (often like English the/that). Use itu if the listener knows which drawer you mean (previously mentioned, pointed at, or contextually clear). Use ini for something near you or just identified.

Could I say Di laci kecil ini instead?

Yes. Di laci kecil ini means in this small drawer (near the speaker or newly introduced as “this one”).

What is selembar, and why not sebuah?

Selembar is a classifier/measure word for flat sheet-like things (paper, sheets).

se- means one; lembar is the classifier → selembar = one sheet.
Correct: selembar kertas, dua lembar kertas.
Do not use sebuah kertas for paper; buah is a general classifier for items but not for sheet-like things.
Near-synonyms: sehelai kertas (also acceptable, a bit more literary), secarik kertas (a small slip/scrap of paper).

Can I just say ada kertas without selembar?

Yes. Ada kertas means there is (some) paper, without specifying quantity. Ada selembar kertas emphasizes exactly one sheet.

Should it be di laci or di dalam laci?

Both are fine, with a nuance:

di laci = in/at the drawer (default, perfectly natural).
di dalam laci = explicitly inside the drawer (adds inside-ness emphasis). Avoid pada laci for physical location; pada is used in formal contexts and for time/abstract relations.

What does untuk menulis do? Is it like a purpose phrase?

Yes. untuk + verb expresses purpose/intended use and here modifies kertas (paper).

kertas untuk menulis nomor ojek = paper for writing the ojek number. Registers:
Neutral: untuk menulis
Colloquial: buat nulis
Formal: guna menulis You cannot use agar/supaya in this slot; those introduce purpose clauses, not noun modifiers.

Can I use menuliskan instead of menulis?

Often you can, but the nuance differs.

menulis nomor is the default: write a number.
menuliskan nomor tends to highlight writing something for someone or onto a target.
- Tolong tuliskan nomornya di sini. (Please write the number here.) — very natural with a target or beneficiary. Without a second object or target, menulis nomor is more neutral.

Does nomor ojek mean phone number or license plate? Is it natural?

On its own, nomor ojek is ambiguous. Prefer a specific noun:

Phone number: nomor telepon ojek / nomor HP driver ojek (colloquial).
License plate: nomor polisi (nopol) motor ojek / nomor kendaraan.
Booking code/order number: nomor pesanan / kode pemesanan. Use the one your context requires.

What’s the difference between nomor, angka, bilangan, and jumlah?

nomor: a label/ID (house number, phone number, jersey number).
angka: digit/figure (0–9), also numerical figures/statistics.
bilangan: mathematical term for number (rare in everyday speech).
jumlah: total/quantity. Here you want nomor.

What would a more casual version of the sentence look like?

Examples:

Di laci kecil itu ada selembar kertas buat nulis nomor ojek.
Ada kertas buat nulis nomor ojek di laci kecil itu. Casual features: buat (for), nulis (colloquial for menulis), no comma.

Any more formal alternatives?

Di laci kecil itu, terdapat selembar kertas untuk menulis nomor ojek. (terdapat is a formal alternative to ada.)
If the paper is already known/specific: Kertas itu berada di laci kecil itu. (berada = be located; then you’d typically state its purpose in a second clause if needed.)