MacOSX Server
Mac OSX comes with a built in web server, although it's not running by default. Starting the web server can be done by running:
sudo apachectl start
To start the server, you'll be asked for your user's password.
Opening your localhost will show you 'it works!', which will tell you that much - it works.
The folder to put files in is
/Library/WebServer/Documents
You may wish to create a subfolder for the firmware files.
Use the IP address of this local web server to OTA flash Tasmota. You can determine your IP address here. For example,
http://192.168.1.123/tasmota.bin
Issue this command to stop the web server when your are done flashing:
sudo apachectl stop
Note: The MAMP web server does not seem to deliver the results as expected!