We've had an ocean plait mat in front of our kitchen sink for over a year now. While the ocean plait is a nice mat, I have always wanted something that is a little more substantial and that is rectangular shape. There are plenty of larger mats in the Ashley Book of Knots. For this mat, I took the pattern out of Ashley (2272), redrew it using AutoCAD and created the step-by-step tying grid that is shown in the attached drawing to make it easier to follow. The redrawn grid helps to set up the mat so that the spacing is closer to the competed mat, which means less time fairing it- Fairing can be a lengthy task on a mat this large. Note that I purposely left some space between each set of passes-* Manila rope is made of natural abaca fiber. When it gets wet, the fiber will swell which will cause the strands to twist and tighten, thereby causing the mat to shrink, especially once it drys out. If I use the mat outdoors, the spaces will allow for all of that to happen and the spaces will close. I used a peg board with some peg board hooks to make it easier to create this mat and keep it relatively straight. Spring clamps and weights are helpful to keep strands in place. This mat pattern is also presented in "Knot Craft" by Des Pawson, with a similar step-by-step method for tying the mat. While I didn't use the instructions in Knot Craft for actually tying the mat, I did find a method in the book for splicing the ends into the adjacent strands. I've traditionally seized my mat ends to the adjacent strand, either with cordage or more recently with zip/cable ties. However, using a splice makes the ends minimally visible, and therefore the mat can be flipped over and used as a double sided mat. A fid makes the splicing go faster, but it can be done without. This mat was tied using a little less than 150 feet of 1/2 inch manila rope.
*A warning about manila rope- Manila rope is treated with mineral oil which may cause discoloration of the floor on which it sits. Consider the surface on which you are putting the mat, or I would suggest getting a pad.