Okay, I finally figured out what you're asking and where you might be getting holes. You're not 'picking up' when you make the first set of triangles, you just add a stitch from the cast on to the block of stitches. This can leave a hole if the cast on is tight - it should be very very loose. A knit CO works better for beginning entrelac than the others - a loose one. Say you start with k2, turn, p2. Next row, you k3, the 3rd st is from the cast on, turn p3, turn k4, turn, etc. That may make a small hole where you've turned to do the purl rows. So if you want to slip the first st on the purl row, that can help 'even' out the transition.