Hand-building guide

How to make a slab box template with a lid

By Slab Marks · Updated October 2026

The short answer: a slab box is six rectangles: a front and back (width × height), two sides (depth × height), a bottom and a lid (width × depth), each scaled up for shrinkage. A box that should be 5 × 3.5 × 4 in after firing, in mid-fire stoneware, needs panels cut to 5.68 × 3.98 × 4.55 in.

Want a different size, or a box without a lid? The free Slab Marks template maker draws the panels for you. See how it works ↓

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The six panels

PanelSizeFor a 5 × 3.5 × 4 in box (cut size)
Front and backwidth × height5.68 × 4.55 in
Left and right sidesdepth × height3.98 × 4.55 in
Bottomwidth × depth5.68 × 3.98 in
Lidwidth × depth5.68 × 3.98 in

Mid-fire stoneware (~12% shrinkage). Cut sizes are the box's outside measurements.

For an open box, a planter or a pen pot, leave out the lid. You can also leave out a side to make a wall shelf or display niche.

Box sizes by clay type

The same 5 × 3.5 × 4 in finished box, in different clays:

ClayWidthDepthHeight
Earthenware ~7%5.38 in3.76 in4.30 in
Mid-fire stoneware ~12%5.68 in3.98 in4.55 in
High-fire stoneware ~13%5.75 in4.02 in4.60 in
Porcelain ~15%5.88 in4.12 in4.71 in

More on why the panels get bigger in how to calculate clay shrinkage.

Joining the corners

The panels are cut at the outside size of the box. To keep that size, bevel the edges that meet at 45° so each corner closes neatly without the slab thickness adding to the width. If you'd rather butt the edges, trim the panels that sit inside by one slab thickness.

  1. Let the panels firm up to leather-hard, so they stand flat and square.
  2. Bevel the joining edges, score and slip them, and press the walls together around the bottom.
  3. Press a thin coil of soft clay into each inside corner and smooth it to strengthen the join.
  4. For the lid, add a small flange or a few clay tabs underneath so it can't slide off.

How to do it in Slab Marks

  1. On the homepage, pick Box.
  2. Enter the finished width, depth and height. Each field says which panels it changes.
  3. Under Leave open, keep "None" for a closed box with a lid, or leave out the top, a side or the back.
  4. Pick your clay under Clay body, click Print template and print at 100%.
The Slab Marks template maker showing a box net: front, back, left, right, top and bottom panels laid out as a cross
The default 5 × 3.5 × 4 in box: all six panels, scaled for shrinkage. The top panel is the lid.

Common questions

How do I make a slab box with a lid?

Cut a lid the same size as the bottom, and add a flange or small tabs underneath so it stays in place. The template maker includes the lid unless you choose to leave the top open.

Can I make a planter or an open box?

Yes. Leave out the top panel. For a wall shelf or niche, leave out a side or the back instead.

Do the panel sizes include the slab thickness?

The panels are the outside size of the box. Bevel the corners at 45° to keep that size, or trim the inner panels by one slab thickness if you butt them together.