kalispell, montana, help with building cob

Hi everyone...I am located in the beautiful Flathead Valley, a couple hours north of Paul in Missoula. I am new to the site and I am hoping to learn how to construct cob for building purposes. I noticed that I just missed a recent workshop. I hope to be able to attend one in the future Lord willing. My question is fairly simple. What is the easiest method to find the clay for the cob mixture? Thanks in advance for any responses.