One of the basic functions of any game is being able to save it unless you are playing a roguelike. The Survivalists is not a roguelike and instead aims to live after ending up on a desert island. Because nothing is easy when you are fighting for your life, you can't just save your game, instead you have to engage with some of the game mechanics to build yourself a way to do it.
To save your game in The Survivalists, you will need to make a bed. This is quite a complex process, so we'll go through it step by step.
Step 1 - The hand ax
The first thing you need to do is the hand ax. This is made of two pebbles that you can find all over the island. Just press C to bring up the crafting menu, then click on the hand ax icon to build it.
Step 2 - Straw and Rope Bundle
Then you need to make a bundle of straw and rope. You can make the straw bud by using your hand ax to break up a bush or tall grass and using the long grass that falls. The rope is made of two long grasses, while the bundle of straw is made of three long grasses.
Step 3 - Comfortable padding and makeshift bed sheet
Now is the time to make some comfortable padding. You will need two long grass, a bundle of straw, a rope to do this. You will need three more long grasses to make a sheet.
Press R to open the build menu, then select the fragile bed and place it where you want it. When choosing a place to build it, you will then need to interact with it and place the comfortable padding, then make the bed itself and finally place the sheet. You can then jump into bed and have the option to save, sleep, or do both.