I always loved preparing a picnic! Whether it was hamper for Glyndebourne (back in the day - nostalgic emoji) or a day out with the girls and the dog.
Home made soup in flasks, a flask of coffee, home made sausage rolls in Tupperware boxes, likewise sandwiches, perhaps flapjack or muffins - always far too much! Crisps especially Pom Bears if there is a small person present, also fruit juice in cartons or water.
Best recently was in a chilly country park before Christmas - celeriac soup, smoked salmon and cream cheese on soya and linseed bread, sausage rolls, chocolate brownies - all eaten at a picnic table with threatening rain but what made it special - with D, SIL and GS who had driven up from London for the only way we were legally able to meet!
When the children were small I would butter and fill sandwiches from a whole loaf of Mother’s Pride then use the wrapper to put them in. It was really satisfying.