There is a few ways to prep the soil. One way is how you are thinking about doing it. I would modify it a bit. Round up works best on actively growing plants. Wait until the weeds are growing and then hit it with Roundup. Wait at least 2 weeks before planting so that the chemical is out of the soil.

Another way it to disc the area a few times. Disc the field and wait 1 - 2 weeks then hit it again. Come back in a week or so and disc and plant. This turns over the weeds and kills them from exposure.

Before you fertilize I would get a soil test done. This will tell you how much lime and fertilizer the soil needs.Take the test results to the farm store and they will blend your fertilizer, and make sure you tell them you are planting clover.If you fertilize when you plant use a low nitrogen fertilizer. The clover will fix its own nitrogen as did the beans. By adding more than needed to the soil at planting, the weeds will take off and out compete your clover.

You can plant clover veryearly in the spring. However, it will not sprout until the soil warms up.Frost seeding is usually done on exsisting plotsor pasture field to help improve the the area with the addition of clover. For proper plot establishment, I would work the soil as soon as it can be done in the spring. Again check with the local farm store or your state's department of agriculture for info. Clover needs a firm seed bed and about 1/4 inch of soil contact, so do not bury it too deep.

I prefer the White clovers for a food plot. They are not "cattle" cloversand are more digestible for deer. I use 2 - 3 varieties in a mix. I also like to add either chicory or Birdsfoot trefoil to the mix along with a small amount of a forage rape. As for the rape I choose, it isbased on the maturity date and when I plan on using the plot.

Make sure that the innoculant on the seed is fresh otherwise innoculate the seed yourself.

Good Luck