1. Finish the shape you want to print
Work from simple mesh objects and keep an editable .blend file. Decide which pieces belong in the export. Remove stray objects that are only references or tests. If you used modifiers, check the resulting shape as it will be exported.
2. Check dimensions and geometry
Measure the object in the units you intend to use. An STL does not carry a reliable unit setting for every slicer, so confirm the size again after import. Look for holes in surfaces, accidental internal faces, and paper-thin features. The printability checklist walks through these checks.
3. Export the STL
Select the printable object or objects. In Blender, choose the STL export option from the File menu, choose a clear filename, and review the exporter options. Use selection-only export if you have reference meshes or other objects in the scene. The exact menu wording can change between Blender versions.
4. Open the file in a slicer
Import the STL into your slicer and check its reported dimensions. Look at the placement on the build plate, support needs, thin areas, and layer preview. If it is unexpectedly tiny or huge, fix the scale before printing. If a feature disappears in preview, return to Blender and adjust the geometry.
Keep the editable source
Save the .blend project as your master file. STL is great for passing shape to a slicer, but it is not a convenient record of how you built the design. For a broader route through modeling and print prep, read the Blender for 3D printing guide.