We've done that, built some raised beds last winter- just put them straight on the grass, covered with cardboard, horse poop, rabbit poop from the neighbours, bit of soil from another bed and a bag of compost. Worked fine this year for lettuce, beetroot, kale, strawberries, beans etc. There's a good video of Charles Dowding doing this somewhere.
We've done that, built some raised beds last winter- just put them straight on the grass, covered with cardboard, horse poop, rabbit poop from the neighbours, bit of soil from another bed and a bag of compost. Worked fine this year for lettuce, beetroot, kale, strawberries, beans etc. There's a good video of Charles Dowding doing this somewhere.