Bring a picnic mat.
Picnic mats come in many specifications. The common ones are 175cm long x 150cm wide and 180cm long x 200cm wide, which are enough for 2 people.
Picnic mats, multi-functional blankets, seat cushions, etc. are velvet fabrics with waterproof bottoms for picnics. They can be rolled out at any time outdoors to provide a clean space for picnics or leisure.