3 orthogonal slices is very sparse data for creating a 3D segmentation but there are some tools in 3D Slicer that can help.
First of all, you need to create a master volume that is large enough to contain your final segmentation result. You can use Crop volume module to create a new volume based on an existing single-slice 3D volume, just by making the region of interest box large enough.
If you have projection images, you can create a 3D model by using Scissors effect. On the first projection you use “Fill inside” mode then on all other slices you use “Erase outside”. We used this to reconstruct breast tumors from a few X-ray projections. It did not produce accurate segmentation, but it showed very nicely how limited amount of information is in these few projections.
You may also try “Surface cut” effect (provided by SegmentEditorExtraEffects extension). This allows you to create 3D segmentation by marking points on arbitrarily positioned 2D slices. We use this very successfully to create breast tumor models from tracked free-hand ultrasound images.