Thanks Ben and @refa42 for the start.
Blender 2.76b
- Add > Mesh > Plane
- Scale and orient as desired
- Place where you want to cut
- For precise placement:
- Right click on plane to select
- Display and edit object (orange cube tab in properties)
- Change location, rotation and scale as needed
- Select model to slice (right click or left click in "All Scenes" tab of Outliner)
- Display and edit modifiers (wrench tab in properties)
- Click drop-down for "Add Modifier"
- Navigate and click: Generate > Boolean
- Operation: Difference
- Object: (Select plane name)
- Shift+d (duplicates selected object)
- Left click to place exactly where the other one is (don't move mouse just left click)
- Under modifiers tab click apply
- G to move and place (or use precise placement in step 3 above)
- Rename
- In outliner window under "All Scenes" change modifier from Difference to Intersect
- Apply modifier
- If making multiple cuts, duplicate plane move
- Shift+R replicates
- I like to delete plane already used