Here's another: Begin by tying off to the first stake. Weave like normal. When you get back to the beginning, instead of tying off to the post tie a taut-line hitch around the twine/rope that you started with.

Instead of having to use a stick and twist it to tighten it, you just pull the knot farther up the line as the twine stretches. This type of knot can easily be slid up the line but when tension is on it it doesn't move.

Here is a link that might be useful: How to tie a taut-line hitch (I use #1800)

Thanks for reminding me of that one.

Not sure how well it will work with crudely made sisal but while looking at your link I found this one.

Here is a link that might be useful: Animated Knots by Grog