diff --git a/flang/README.md b/flang/README.md
--- a/flang/README.md
+++ b/flang/README.md
@@ -333,7 +333,13 @@
 ## Generate FIR Documentation
 If flang was built with `-DLINK_WITH_FIR=ON` (`ON` by default), it is possible to
 generate FIR language documentation by running `ninja flang-doc`. This will
-create `docs/Dialect/FIRLangRef.md` in flang build directory.
+create `<build-dir>/tools/flang/docs/Dialect/FIRLangRef.md` in flang build directory.
+
+```bash
+cd ~/llvm-project/build
+cmake -DLINK_WITH_FIR=ON ../llvm
+ninja flang-doc
+```
 
 ## Generate Doxygen-based Documentation
 To generate doxygen-style documentation from source code