I recently finished renovating our kitchen, and one thing we couldn't find was a suitable rack that accommodated all our herbs & spices. Not for my wife a few desultory plastic containers; she has dozens of mason jars in four different sizes that fill many shelves in a normal cabinet and generate a sorting problem when you're trying to locate a herb or a spice you haven't used for a while. Here's my modular solution. Because I've designed it for jars of 4, 8, 16 and 32 oz, you could redo it using any one (or more) of the sizes that best suited your needs.

Step 1: Design

The main idea of a spice cabinet is to present everything so you can see all your options at once, or at least easily access them. I settled on making arcs of jars with all jars of the same size on the same layer. I have access to a laser cutter, so fabricating the shelves would be straightforward. I planned to use the holes drilled inside the IKEA cabinets for shelf support in exactly the same way as they're used for regular shelves.

I used Fusion 360 to design the shelves. I measured the size of the cabinet (it's nominally 18" wide, 15" deep and 40" high) and drew a rectangle, then measured each jar and calculated how wide the shelf needed to be (giving some space around each jar). That defined a distance for the sides at the front and the middle at the back. The easiest way to produce a smooth arc was with the ellipse tool, and I drew three: one to define the front edge, another to define the midpoint of the circle that would hold the jar, and a third for the back of the shelf. I then drew a circle large enough to hold the base of the jar on each side. I measured the length of the remaining arc and calculated how many jars I could fit in, then divided the distance evenly by that number. It worked out that I could fit 9 small or medium (4 or 8 oz) jars, 7 large (16 oz) jars, and 5 very large (1 quart) jars. Aesthetically this was nice because there was always a central jar at the back.

All four shelves are attached to this step as .dxf files for cutting. Note there are two shapes for each shelf: one is to be cut out of 1/4" (6 mm) plywood for the base of the shelf, and the other out of 1/8" (3 mm) plywood for the rings.

Note: we have 4 different sized jars for historical reasons, and the larger ones are for herbs that we grow in our garden. I suggest if you're making this yourself, pick the most practical size for you (I recommend the 8 oz "medium" sized jar) and stock all your spices in those (double-up when you need to). If you have a router and want to save money on laser-cutting, just laser cut one of the horseshoe-shaped holey parts and use it as a template - you could do something quite cool then and rout out each spice shelf out of 3/16" plywood and cut the holes to a fixed depth. No gluing!

Step 2: Cut

Cut out all the shelves with the lasercutter of your choice; I used a Trotec Speedy360, which with a 130 W laser makes short work of the job. I could cut two shelves per partial sheet of plywood (not very efficient, alas). Using wood glue and clamps and weights, I glued up the two parts of the shelves (I have an instructable on improvised woodworking clamps).

Step 3: Glue and Finish

I primed the shelves, sanded, then painted with several light coats of white paint, sanding between each coat, until I was happy with the finish. I think this was 2 or 3 coats plus the primer.

I then clamped pairs of shelves together to drill holes for the shelf support pins. Measure carefully for this and mark the center of the hole with a nail before drilling - it's easy for the bit to wander. This approach is the easiest way to cut semicircular notches.

Step 4: Add Jars Etc

Once you've decided how you want to organize your herbs and spices, label the jars and add the contents. Note the space where the hinge is no longer fitted a jar, so we put a wee mortar and pestle there instead. All of our jars were labelled by my wife's impeccable hand.

Step 5: Done!

Organizing this sort of cabinet is very much personal preference. If you choose to make one like it, I'd love to see it - post a picture and I will send you a premium subscription to instructables.