Making cob by foot is really easy. If you have a tarp and spades that is preferable but not essential.
Firstly get your sand and clay ready. A good cob is made from between 70-85% sand and 15-30% clay with long straw or other available fibre, and water.
Mix you clay and sand together till they are a good homogenous mix. If you are mixing on a tarp you can pull at two corners and roll it around to get a real consistent mix.
Next add your water till you have a nice cob. It should not be too wet or too dry, and should hold its shape when made in to a little sculpture for example. Roll a sausage and hold it between your finger and thumb with about 2.5cm protruding from your fingers. If it breaks it is probably too wet or dry, add water if it is too dry, or hope that when you add the straw it dries out enough to use.
You can check if you have enough straw in your mix by grabbing a big lump and making it into a ball. Break the ball in half and if there are a lot of pieces of straw sticking out you are on the right track, if there are only a few then you need to add more.
And that is all there is to it really. It helps to make your cob next to where you are building as it is very heavy to move after it has been mixed. If you are not right next to your house then you could make a line of people throwing big balls of cob to each other. Have one person as the wall placing the balls as they go. Once a whole layer of balls has been placed you can get to work integrating them in to the wall.
Any questions please leave them below.