"in-depth advice" is correct and usable in written English.
You can use it to refer to advice that is thorough, detailed, and comprehensive in nature. For example, "The lawyer gave me some in-depth advice about how to proceed with my case."
In this essay, Mr. Barnard provides more in-depth advice about visiting college campuses this summer.
For more in-depth advice on the day, you can book an appointment with one of the C2 consultants (£25 for a 25-minute-session).
Whether you work in marketing or PR, or want to grow your own business, you'll receive in-depth advice on how to create great Instagram images and build communities around your brand.
Authors of the new-and-improved approach worked with members of the local trans community and looked to international standards to shape the in-depth advice.
The Internal Revenue Service government website offers in-depth advice for choosing a tax advisor and provides forums to file complaints or reports if any issues arise.
A panel discussion further provided in-depth advice on advancing development of personalized cancer medicines in China.
It's called "Steps in Overcoming Masturbation" and gives in depth advice on how to overcome its evil and impurity.
To get some in depth advice I interviewed Olga Kay, YouTube celebrity-turned-entrepreneur, about her sock company, MooshWalks.
In addition, patients may recall receiving small pieces of advice from their GP in our study but the 'counselling' may refer to more in depth advice.
Best: Sophisticated in-depth testing.
The focus of this consultation on this occasion was clearly relationship building, where the GP appeared to have prioritized active listening and relationship building, at the expense of in-depth history taking, advice, brief intervention or even reinforcement of the stated motivation to stop smoking.
