This constructions consists of 4 modules. Refer to those modules for detail info on how to make those individual modules. 

The objective was to build a table from a 6ft x 4ft plywood sheet and only use that material. 
The size of the table - 3ft x 4ft. 

1) Top surface - 3ft x 4ft - 122mm x 91mm  - 1no
2) Legs - 15mm x 80mm - 4nos
3) I beam - 15mm x 72mm - 1no
4) Base board - 15mm x 45.5 mm - 2nos

All the wood required needs to be cut out from one sheet of 4ft x 6ft. This design fits in on one sheet. 
Using a pencil mark and cut the 4ft x 6ft sheet as shown in this image. 

Build the leg module and attach the base module to it. Refer to the Leg module documentation for details on assembling the leg subassembly. 

Attach the leg module to the top deck using 35mm screws. Here is the reference diagram


When you are assembling, attach both leg subassembly to the top deck first. Then screw in the I - beam to both the leg assemblies. This will make sure that the everything is in alignment.