"match" not subfolder

[BrentH-Alnico]

Need to NOT match filename contained in subfolders...
Match index.html but not /subfolder/index.html
This Regex does not work: ^[^\\]*\\index\.html$

Is there a way to do this? What 'flavor' of regex is supported?
Thanks.

[mygoodboy]

it seems need double \
it's working .*vscode\\\\settings.json for me