Work 1 row of the shell pattern. You will be adding a block and a space at the end of each row. Each row will end in the same manner setting up a space and a block for the next row. Ch 10 and turn. (the first ch 3 will be the base of the block, the next ch 2 will be the base of the space, the next ch 3 will be the turning chain which counts as the first dc of the space, the next ch 2 will be the top of the space.) Turn and insert the hook into the 8th ch from the hook and dc. Dc in the next 2 ch, and complete the block by working into the last dc of the previous row.
Continue in this manner, working spaces and blocks and the shell stitches as established. As you complete each row, the last stitch will be a space and to create a block over this, dc in the last dc of the block in the previous row and work 3 dcs into the space before adding for the next row.