Guinea Fowl start laying at the start of April and will lay most days until early October, depending on the weather. One hen bird will lay up to 100 eggs a year, although I find that 50 or 60 is more normal.
They're not fussy about where they lay their eggs and you'll find them under bushes or even on open ground. When they decide to build a nest, they will pick a very well hidden spot, usually in some long nettles! Here they scrape a shallow hole in the ground and will lay an egg in the nest almost every day.
The birds will usually all share one nest, sometimes two birds will sit at the same time, otherwise they form an orderly queue.