Worked with two strands of thread, or, thread doubled.

Bedspread weight crochet cotton (Size 10)
Size 0 steel hook (or size required for gauge)

Gauge
With 2 strands of thread, center shell strip = 1.25” x 3.25”

Center of the doily is worked flat, back and forth in rows. Pineapple border is worked in the round.