The whole of S. W. Lancashire is covered in a sheet of clay left by the ice age. Roving brickmakers made bricks for customers, usually using clay from a local field (and coal from the Skelmersdale area). You may find it interesting to read the diaries of Nicholas Blundell of Little Crosby (he called them Diurnals). In them he outlines the whole procedure (& costs) for making bricks in the early 1700's.