"Prompted by the arrival of our fabulous linen sheeting range," this shop has instructions and measurement charts for making fitted sheets for mattresses of many sizes. Sadly for me, the shop only sells the linen in-country, and they're in Australia.
UPDATED ~ TUNISIAN ~ Are you a beginner at Tunisian crochet? We've got a pattern especially for you: the Honestly Easy Tunisian Crochet Afghan Pattern. You won& have to be nervous to try this pattern because it& made as an intro to Tunisian crochet.