Is "sound approach" an accepted phrase?

English is not my first language, and in my language (Bosnian) we write just as we speak ; so from time to time, I encounter phrases which I know I have heard before, but am not sure if I am writing them correctly.

Do you say sound approach to describe an approach to a problem which is logical, makes sense, and is practical?

The reason I ask is that I could not find it in a reliable online reference, and I have a feeling that I am spelling it wrong.

Used as adjective, sound can per the OED mean:

In full accordance with fact, reason, or good sense; founded on true or well-established grounds; free from error, fallacy, or logical defect; good, strong, valid.

And it is this sense that is operative here. They give four citations that appear especially relevant, albeit not especially recent:

• C. 1440 Capgrave Life St. Kath. ᴠ. 1183 ― Youre counseyll in this is neyther saue ne sounde.
• 1576 Gascoigne Steele Gl. (Arb.) 52 ― And sound advice might ease hir wearie thoughtes.
• 1596 Edw. III, ɪ. i. 101 ― The soundest counsell I can giue his grace, Is to surrender ere he be constraynd.
• 1697 Dryden Æneid xɪɪ. 42 ― Sound Advice, proceeding from a heart Sincerely yours.

In summary, I should say that your approach is therefore sound.

Yes, a sound approach is accepted and idiomatic English. Here's what Merriam-Webster says about sound:

3
a : free from error, fallacy, or misapprehension [sound reasoning]
b : exhibiting or based on thorough knowledge and experience [sound scholarship]
c : legally valid [a sound title]
d : logically valid and having true premises
e : agreeing with accepted views : orthodox

You should try the dictionary before asking. Then ask a search engine to answer your question. Google, for example, show about 71,900,000 hits for a sound approach. They usually help and preclude the need to ask for help from others. We have this famous old saying in English: God helps those who help themselves. It's a platitude, but one worth testing every day.