To make the tartar sauce, finely mince 1 clove of garlic and add it to a mortar, then add 1 tablespoon of capers and using a pestle mash down on the garlic and capers until you form a paste, next add 1/2 cup of Greek yogurt, 1/2 tablespoon of dijon mustard, 1/2 teaspoon of white wine vinegar, season with sea salt and freshly cracked black pepper, and mix everything until it's well mixed, then cover the mortar with seran wrap and add it to the fridge (spainonafork.com)
To prepare the avocado simply mash it down with a fork and add the lemon juice and salt. (happyskinkitchen.com)
Once the potatoes have cooled place them in a large bowl and with a potato masher mash them down as best as you can. (happyskinkitchen.com)