i love sheet mulching. i sheet mulched my whole garden this summer and will keep doing so until all of everything is growing food!!! i'll tell you about how i would do it next time, because i messed up a bit. so... if i were you i would start by identifying ALL the area you want to mulch and cover all of that (including the paths) with 2 layers of cardboard. if it ends up with some 3 or even 4 layer areas that is ok.
and then you basically go green, brown, green, brown, etc. you want to have approximately 1:3 ratio of green/nitrogen : brown/carbon. so i used twice rinsed seaweed (green), fluffed hay or straw (brown) [if you use hay, you
MUST cover it all with the future layers or you'll end up with grains growing like grass in your garden.] grass cuttings (green, if dried out - they still count as green), i used peat moss but i wouldn't again - expensive environmental impact. chicken or other manure counts as green because it's so high in nitrogen. slashed vegetation from that spot or another counts as green of course. dried leaves are brown. etc. sometimes i would have two layers of hay seperated by seaweed for example - you just keep going because you want it to be at 12 - 24 inches thick for good root space for root veg. Please note that root vegetables do NOT grow in this the first year - the roots hit a nitrogen layer and stop growing - you end up with great tops but no carrots for example!
Be sure to SOAK each layer
as you go with water - it needs the water to break down - and it will save water later. if you have top soil or finished compost from previous years, use that for the top layer.
some people then use straw on top of that for mulch (keep weeds down and moisture up) but i like a living mulch like clover, which traditionally we've been taught to keep out of our gardens. it maintains a nice moist ground and you just pull out a clump for a seedling to replace the clump or pull out small strips for planting seeds and then the dutch white clover (perennial) is there to keep everything moist. now my land is quite dry so from june through september i am worried about water - you may be in a wetter situation, even if it has been too wet - you now basically have raised beds so they will be dryer than your normal.
one thing i forgot to tell you -
imagine your paths as really wide - like plan for 2 foot wide paths if you want 12 inch paths - because the rate of fall for the ingredients will create an angle that falls into the pathway.
i cardboard everything now for a few reasons: 1. the elements of the layers will fall onto the path - so if there's no cardboard on the path but there is a growing medium - there will be grass and weeds coming up. 2. you may change the design/pattern at some point and it's a hassel to have to move the layers to re-cardboard an area - this way you can just push it over to a cardboarded area - the cardboard will break down under whatever you cover the path with. 3. it's easier to ensure full coverage - especially with rhizome plants like grass - they sneak underground to start new plants. it may still happen because the layer ingredients may have grass seeds in them but if you pull the grass out throughout the first year, you'll have very little problem later - because the grass deals with root fatigue (the roots need the nutrients and energy harvested by their leaves - no leaves no energy!)
groundcover and a living mulch are the same thing except that usually people think of groundcover as temporary like through the winter, which is good too. however using it as a living mulch is cool because that plant (i'm using white clover (4-6 inches high) so it's a perennial and nitrogen fixing like beans) will shade the ground (keeping it moist), will nourish the ground year-round, the flowers attract beneficial insects, and it suppresses weeds! all good - a no weed garden, a japanese man, masanobu fukuoka, called it a do-nothing garden!!
if you're looking at doing this in the fall - that would be great - you don't have to water so much because it'll be raining/snowing and then in our neck of the woods, you can plant garlic right away for next september and an annual ground cover so you have time to plan what you want to do: like perennial live mulch vs. annual?, what plants where?
remember to allow space for permanent plants like rhubarb or asparagus or artichokes for example. also remember other plants should all be rotated to avoid bug problems.
