Learn Hardcore Indonesian: Adik laki-laki saya mencadangkan catatan kuliah setiap hari. - My younger brother backs up his lecture notes every day.

bold adik bold = younger sibling (gender not specified)
bold laki-laki bold = male Putting them together, bold adik laki-laki bold = younger brother. If gender is already clear from context, bold adik saya bold is enough. For “younger sister,” say bold adik perempuan bold.

Why is bold saya bold after the noun phrase instead of before it?

In Indonesian, possessors usually follow the noun: bold adik saya bold (my younger sibling), bold rumah saya bold (my house).
You can also use the clitic bold -ku bold:

bold adikku bold = my younger sibling
If you keep the gender word, write bold adik laki-lakiku bold = my younger brother

Can I say bold Adik saya laki-laki bold instead?

That forms a clause meaning “My younger sibling is male,” not a single noun phrase. To use it as the subject of this sentence, you want the noun phrase bold adik laki-laki saya bold.
If you’re distinguishing among siblings, you can also say bold Adik saya yang laki-laki … bold (“the brother among my younger siblings …”).

Is the hyphen in bold laki-laki bold required? Can I just say bold laki bold?

Yes, the hyphen is standard spelling. bold laki-laki bold is a fixed reduplicated form meaning “male/man.” Plain bold laki bold by itself tends to mean “husband” in informal speech and isn’t used here. A single-word synonym for “man” is bold lelaki bold, but for “younger brother” you typically say bold adik laki-laki bold.