Your friend creates the hotspot, you connect to it like any other WiFi network and then for the address, they enter the IP of your phone which is shown on the lws app or it can be scanned as a qr code. (It doesn't work for some reason, if you create the hotspot. I don't know why. I edited my previous post to correct this detail)
Not OP but I would try something with a .1 ending, deriving the first three bytes from the client phone's IP. Although, when creating a hotspot, Android might make a new network namespace for it so you still wouldn't be able to connect to the web server.