This is more of a culinary suggestion than a recipe; though, I suppose all recipes are essentially suggestions, so this is no different in that respect. Putting it another way, I might have said, this is less of a recipe, than a culinary suggestion...
In recipes, one is usually required to combine ingredients somehow, in a more or less strictly prescribed way; although, the best recipes still allow room for a bit of artistic freedom. Here, the fun lies in everybody doing things themselves in whatever order or combination they wish. The task of the cook is simply to boil the potatoes, wash and trim the salad vegetables, then present everything in an attractive way (So, there's still some scope for individual expression). But your guests do the rest off the work. They peel their own potatoes, grab a cucumber or maybe a green onion, and then dip it in salt or sour cream.
This is a nice outdoor recipe. The potatoes can be served hot or cold, so it would make a good picnic. We used to do it a lot on our dacha, using fresh produce from the garden. We had tomatoes and chilli peppers too and you could of course add those and any other vegetable you fancy to the selection. I just put the ones below in the list because I think they are traditionally the most common in Russia, where the summers are relatively short and cool and tomatoes and peppers don't do so well.
2 or 3 large smooth-skinned potatoes per person
A large bunch of green onions
A bunch of fresh dill
A bunch of fresh parsely
A few cucumbers
A load of radishes
A pot of sour cream
Salt
Scrub the potatoes to remove any dirt and put them in a large pan of water. Bring to the boil and salt, then simmer until the potatoes are soft enough to stick a fork or knife in easily.
Wash all the vegetables and trim the green onions, dill and radishes as required. Serve everything on separate plates, bowls (including a small bowl of salt). Everyone can then help themselves to whatever they wish.
If you can find some black (rye) bread, I would recommend putting some of that on the table. For a drink, why not serve a big jug of cool fruit compote and of course, for authenticity, a bottle of chilled vodka, straight from the freezer (or from the stream, if you're having a picnic.