http://katiesquiltingcorner.com/2012...-tutorial.html
This one is very functional and has a pdf of the tutorial that you can print.
https://www.bing.com/images/search?view=detailV2&id=31210C68F322458A25A3F80480691AC9B268B9A8&thid=OIP.gQmaEQL02gjJ6_vtHKEGrAHaFt&exph=617&expw=800&q=sewing+machine+mat+free+pattern&selectedindex=4&vt=0&eim=1,6
This one is only a picture but could be figured out easily -