As a seller, you can build a product that contains multiple products with different options. Allow the buyer to design his product by himself.
For example: when buying a computer, the buyer will have the ability to choose from different components options. Hard Desk type and storage, Ram size, screen type and size, and so on...
First step: Add the products as simple products separately
You can add a Zero in price for any product (If you will give this product as a gift in custom build product and choose unlisted), and it will appear (Free) in your store while building the product

Add Zero in price then, Add Product

(PS, that if you choose the status to be Unlisted, that means, this product will appear only in the custom build product and the buyer can't buy it separately)
Second step: Add Computer product as a Custom Build, not a Simple product

Add the image if available, then go to Categories and Manage
Add new category
Name it, add an image
Answer these questions, then Add
The 1st Q means that you will allow the buyer to choose more than 1 option in this category or not
The 2nd Q means that if it's mandatory for the buyer to choose 1 option at least, or he can skip this category
The 3rd Q means that if you will allow the buyer to choose multiple numbers of the same option or not according to the inventory of this item
(PS. If you choose Multiple choice in the 1st question and Yes in the 3rd question, you need to limitate the maximum Number the client can use)
Click on Select products
Select the available products in this category, then Add
Now, we added all the available screens in this category
(You can make one of these products as Pre-selected by default by hover on the option)
(FYI, this statement appears in this category, as you answered Yes in the 2nd question above)
We'll add a new category now for Hard disk, by clicking on Add new category
Name it, put an image
Answer the same 3 questions, then Add
Click on Select products
Select the products for this category, then Add
Add a new category of RAM, and put an image
Answer the 3 questions, then Add
Select the products of this category
Then, Add
Now, let's add the last category which is for Keyboard, name it, put an image and answer the 3 questions, then Add
Here, we answered No in the 2nd question to make the buyer able to skip this category if he doesn't need to buy any
Select the products in this category, then Add
Save all these categories we added
Let's Preview the store to see how the buyer will customize his computer
Press on Build your product
Here, you will find all the categories you added to this product
You can choose more than 1 option (Up to 2) in this category, as we answered Multiple choice in the 1st question while creating this category for screens, and It should be 1 choice at least as we answered Yes in the 2nd question
So there is Required label in all categories, we answered Yes in the 2nd Q
We can see that you can increase the quantity of the options we chose, as we answered Yes in the 3rd question in this category
You can see that you can skip this category with no choice as we answered No in the 2nd question while creating this category for Keyboard
27. And this is how the free gift appear on your store

28. After finishing building your product, you'll add this to the cart and go to checkout normally

Use cases for Custom build feature ⬇️