Rule for most plantings are about 2-3 times size ..deep.... ie in this case about 2" deep , horizontal is best, dust with rooting hormone for good results.
4" will also work , but the crown will eventually be at the surface, so well covered below at least 1" works fine.
I dig a small hole about 1.5 length of rhizome, all the rhizomes I am about to plant have been sprayed lightly with water and then put into a bag with some rooting hormone to dust them (just lightly), I then use a large hand of miracle gro soil in base , plant rhizome onto that and add another handful on top, then fill hole with rest of std soil, then - very important compact the soil, I stand on the place I have just planted. Last I cover the new planting with mulch and then water well.
New shoots within a week to 10 days at this time of year.
Note because we have clay, we have worked our soil with lots of organic material to break it up, so when planting I make sure the soil around the hole does NOT have too much clay.
