You will require one dozen of 12-foot logs, having a diameter of 12 inches, for building your raft. Besides that, you will further require two 7 to 8 foot logs, with 4 to 6 inch diameter, to start with.
Place all the 12 logs you have on a levelled ground side by side and make a platform of them. These 12-foot long logs will provide sufficient surface area for the raft to float over water and remain stable as well.
Take an axe and carve dove tail notches into the ends of all the logs you have placed on the ground. Make sure not to cut deeper than 2 inches and start cutting a foot away from the end of each wooden log. The dove tail cut you are making should be about 2 inches wide at the top and should get wider while coming towards the bottom.
Once you have carved the notches, line them up on the logs in a straight line. Make sure you are able to see straight through the line of notches side by side. This step will ensure that all the notches are being place in a line.
Now take the other 7 to 8-inch logs and cut their ends into a triangular shape. Now you can easily insert them through the notches and fit in place.
Take the two smaller logs and slide them between the notches to make a cross beam across the wooden platform. All the logs are now assembled and you just need to keep them in place to complete your raft.
You will need twine to tie up the logs in place. Make sure to wet the twine first, as this will stretch it and you can lash it easily across the beams of the raft body. Keep the twine as tight as possible, so that the logs remained affixed in their true position.