HtmlImport of a web-component

I followed the guide from the docs
[https://vaadin.com/docs/v10/flow/web-components/integrating-a-web-component.html]
(http://)
as good as possible but after a few steps I was unable to continue.
I tried import a leaflet webcomponent like this:

@Tag("leaflet-map")
@HtmlImport("bower_components/leaflet-map/leaflet-map.html")
public class Leafletmap extends Component {
...

In the Chrome console it I always get the error

GET http://localhost:1995/frontend/bower_components/leaflet-map/leaflet-map.html 404 ()

I see it in my external libraries and with the paper-slider it works like a charm but not with leaflet.
At the moment I use gradle not maven, I hope thats not the problem.

Do you have the leaflet-map.html under bower_components? Check in chrome sources tab if the file is present.

Yes it is.

Try putting the folder “bower_components” in the folder “frontend” which is located in the root of your “webapp” folder.