Indefinite Articles

In English there are only two indefinite articles which are "a" and "an". In Bahasa Indonesia there are many. But they are not  differentiated by what sound in the first syllable comes after the articles. They are distinguished by the types of the noun which is divided into three main articles: sebuah (for non-living thing and plant), seekor (for animal), and seorang (for human).

The "se-" morpheme here means satu (one). But you can't use it directly combined with the noun. Because it will mean other things. For example: if you combine se- with rumah (house) it will become serumah which means "living in the same house" not "a house". To say "a house" you say sebuah rumah.
Anyway sebuah is not an accurate way to call any non living things or plants. Sebuah should only be used if you don't know the exact singular indefinite articles for that certain non living thing or plant.

I will show you some common indefinite articles and their noun examples.
Sehelai (a strand) => kain (cloth), pakaian (clothes), kertas (paper), rambut (hair), benang (thread), etc. Usually any thin things you can wave. Your hand is not one of them because it's not thin.

Secarik (a scrap) => kertas, surat (letter). Basically a piece of paper.

Sebatang (a rod/stick) => pohon (tree), kayu (wood), rokok (cigarette), etc.

Sebongkah (a chunk) => batu (stone, the big one), berlian (diamond, the big one), emas (gold, the big one), etc.

Setangkai (a stalk) => bunga (flower), or any kinds of flower: mawar (rose), anggrek (orchid), melati (jasmine), etc.
And many others.

But nowadays, many Indonesian just use sebuah to make it simple in a formal writing even sometimes not specify any articles, let alone in a conversation. For example: "John just bought a t-shirt in that store" would become "John baru saja membeli baju kaos (not specified whether it is one t-shirt or many) di toko itu" in some formal writing and would become "John barusan beli kaos di toko itu" in everyday conversation.