Start with a plan, then build one layer at a time.
Choose a diameter and keep width and depth equal for a circle. Odd diameters have a centre block; even diameters have a centre between blocks. Different width and depth values make an oval. Use the same plan for every quadrant.
Circle generatorStart at the lowest slice and check its footprint before moving upward. Choose a hollow shell or a solid shape. A dome gives you the upper half of a sphere, with an optional base for builds that need a floor.
Choose a picture, set its width in blocks and pick the materials you want. Compare the original with the textured result. For a wall, row 1 starts at Y 0; for a floor it starts at Z 0. The original stays in your browser.
Image to MinecraftWork backwards from finished blocks using complete crafting batches. For example, 65 oak stairs need 17 crafting-table batches: 102 planks produce 68 stairs. Check the recipe method shown by the resource calculator. Most blocks stack to 64, pearls and eggs to 16. A shulker box has 27 slots.
Choose the dimensions, inspect the 3D preview and follow the layer plan. Test a short section first, including headroom above each step and the openings at the top and bottom.
Spiral staircase