A very simple API endpoint for loading and printing files direct. This is by default turned off and it "allowed" via the settings

From within Slic3r adding a post-processing script .bat containing

c:\curl\curl "http://192.168.0.7:5000/api/load?apikey=D96FA6A216CB44F78705D4506689D0EC&print=true" -F file=@%*