This is a simple mat grid spanning 12 bights and 14 parts with an open lattice structure for single string knots. All the smaller knots in this range can be extracted from this grid. Notice that the string crossings are not defined yet, so this grid is uncoded.It was constructed by laying out a series of 10 bight segments on a horizontal line across the top with a 3 bit blank space between each. Then 45 degree diagonals were dropped from each end point of alternate line segments to create the grid structure. When this was cleaned up with the eraser tool from tool bar of Paint, the grid shown was the result. Tip- if you hold down the shift key while using the line function, you get either horizontal, vertical or 45 degree lines, depending on the direction on the mouse travel. The color fill of the grid structure was done after it was constructed and all the holes closed as a matter of personal preference as you can work in black and white just as well. I just seem to visualize the structure a little better in color.
Here is the same grid with the parts and bights numbered. Since my master grids are somewhat larger than this example, I just count the parts and bights by eyeball, but this is to try to make the process obvious. Extracting a knot template is a two step operation. 
The large grid at the right is a fundamental uncoded mat grid with a closed lattice structure. ( In fact it is the previous grid with the paths we left blank now filled in, ) We can now build the skeleton of the primary knot of 9 parts and 5 bights by filling in the intersections of this knot with red color. We go up the right side for a total of 9 parts and the top bight. Since each edge block except the first is an intersection of the parts, we count up 1 - 3 - 5 - 7 - 9 using alternate blocks to leave a space for the interweave of the second knot. Now , again skipping one for the interweave, place the bight boundaries of 5 bights at each edge. Remember that half of the first bight falls on each side of the template at the bottom so we fill 6 blocks at the bottom. With the frame filled in we can now fill the alternate blocks of each column with the red color for a complete skeleton of the 9 X 5 primary knot. What this amounts to is that each intersection of this skeleton, we know that that intersection will be the same color, whether it is an over or an under. 
Now we can frame the 5 X 7 interweave (blue) inside the 9 X 7 primary knot (red) by exactly the same method, bearing in mind that the blue bights nest inside the red bights at each edge. When we fill in the columns under and over these bights, we are left with alternate columns which are not colored. these are the intersections of red and blue which will finally be the color of the part passing over at these points. (Note that we haven't coded anything yet.) That is the next step.
Now we can code the basic skeleton of the 9 X 7 knot in red. This is a matter of following each red part across the knot and coding the U-O-U-O --- pattern of a conventional odd part turkshead on the alternate red intersections. Then filling in the outside red bights around the nested blue bights.
Now we can start the interweave. (note that I coded in an entry point at the blue arrow.) The yellow dot is the actual start and end of the interweave, but in braiding the knot, it helps to have an entry for the string from the edge of the knot. 
Now we finish by coding the white "unders" on the blue leads as "overs on the crossing red strings.
Here are two examples of coding the crossings on an interweave template. The one at the left is a single O-ver going up to the left and the one to the right is a two pass O-ver coming down to the left. Notice that in going over an intersection we remove the inner boundary lines, and going under we remove the outer lines. The coding process is mostly erasure and color filling.
