1. Choose a suitable location: Find a flat area with deep snow that is at least 2 feet deep and has strong, packed snow.

2. Gather necessary tools: You will need a snow saw or a large knife and a snow shovel.

3. Mark the perimeter: Create an outline of your igloo by drawing a circle in the snow with a stick or using the end of your snow saw.

4. Cut snow blocks: Use the snow saw or knife to cut rectangular blocks from the packed snow, approximately 18 inches long, 12 inches wide, and 6 inches thick.

5. Arrange the first row of blocks: Starting at the marked circle, place each block side by side on the inside of the circle.

6. Shave edges for better fit: To create seamless joints between blocks, shave their edges to make them fit more snugly together.

7. Apply slush as a mortar-like filler: Using a mixture of loose snow and water, fill in any gaps between blocks on the inside surface of the igloo wall to reduce heat loss.

8. Begin constructing spiral pattern: The second row of blocks should be slightly more toward the center of the igloo, creating a spiraling construction pattern.

9. Construct additional rows upward and inward: Continue adding rows in this manner until the structure narrows down towards a dome shape.

10. Create a slanting top row for support: To complete the top space, build your final row of blocks slanting inwards to support one another without collapsing.

11. Fit in your last block as the keystone: Carve a block with precise measurements to fit snuggly into the remaining hole at the top of your dome as a keystone, securing it in place with slush mortar.

12. Shovel out excess snow from inside: Once your structure is complete, clear any loose snow that has accumulated on the igloo floor.

13. Create a door: Carve an entryway into your igloo, making sure it’s not too big to retain heat inside.

14. Ventilation: Remember to make small holes in the upper walls for air circulation and air regulation. Your igloo is now complete!