Domum Ornamentum

To start, you need to craft an Architects cutter.

The easiest way to find the materials you need is to hover your mouse over the the image of the requested item. This will bring up an information box, telling you the name of the item, that it is crafted in the Architects cutter, the main material, and the support material(s).

When you have that information, you can put the materials in the Architects cutter. Once you have the materials in place, click on the image of the item in the middle section of the Cutter's GUI, and it will show that item in the output box. Check carefully to make sure the output matches EXACTLY the required materials from the request. Take special care matching the support materials as any differences in materials means your colonists won't use the item you craft, and some of the supporting materials aren't visible from the output preview.

When you have crafters, e.g. a Sawmill , up and running, you can then teach them the recipe by choosing the "custom recipe" tab and putting it in there. Input 1 is the top left slot of the cutter, input 2 is the top right, and input 3 the bottom left slot in the cutter. When you have put the items in the slots, you will see various items below the input slots. The crafter can create ALL of those items from the recipe you have input.

However, crafters can only learn these recipes if they correspond to at least one of the materials. For example, the Sawmill can only learn recipes that involve wood, and the Stonemason's Hut can only learn recipes that involve various types of stone. For recipes involving multiple materials, any of the corresponding crafters work; for example, both the Carpenter and Stonemason can learn Brick Extra-framed Oak Planks (pictured below).