Documentation describes template for setting in Preferences > Build & Run > Default Build Properties. It looks like good default template it actually was in earlier versions which was lost after I upgraded Qt Creator and I wanted to restore.

Suggested template for Default build directory is: 

"build-%{ProjectName}-%{Kit:FileSystemName}-%{BuildConfig:Name}"

Firstly, it uses %{ProjectName} variable which isn't expanded now (variables list doesn't contain it too).

Secondly, such a directory should be placed at same directory level as project, not inside project tree (like it was earlier by default).

Working template to restore earlier default is: 

../build-%{JS:"%{Project:Path}".split('/').pop()}-%{Asciify:%{Kit:FileSystemName}-%{BuildConfig:Name}}