I have a dehydrator but this is my SWAG on oven dehydrating:

Most dehydrators run in the 140-160degF range, so try to achieve that temp with your oven.

Dehydrators take fresh air and heat it, pass it over the food and then expel it to increase removal of water from the product.  Ovens are made to contain the heated air to a much greater degree, so I would say prop open the oven door by, perhaps, closing it on a wooden spoon to get the needed circulation.

Dehydrators use polyethylene sheets/inserts to hold liquid/semiliquid food as it drys.  Even then the "fruit rollup" is fairly well stuck to it.  Milk bottles are polyethylene(PE) so you may try using bottoms of these to hold the salsa as it drys.  How it would work on metal cookie trays is a mystery I am not interested in delving into.

I must repeat that I have not done oven dehydrating since I own a dehydrator, but knowing the physical processes that go on in dehydration this is my best guess at how I would approach oven dehydrating.