I essentially followed this plan by Ana White, but omitted the finials and used 1x2's for the side bars instead of dowels. If you want to replicate this version, you can follow Ana's plan but omit the dowels from your shopping list and add an additional 6-foot long 1x2 to your shopping list. I cut the side bars 7" just like the dowels in her plan.
I used a Kreg jig for all the joints, which I just bought, and am honestly not sure how I ever did any woodworking without it! It is really, really easy to use and makes super strong joints.
For the mattress, I cut a piece of 3"thick high density foam to 12" x 18 1/2" to fit the inside of the crib. I used a spare envelope closure pillowcase for the "sheet," flipping it inside out and sewing straight seams to make a 15" x 21 1/2" square (the extra 3" are to account for the width of the foam. I trimmed the extra fabric from the edges, flipped it right side out, and inserted the foam.
I painted the crib white and stenciled a Fleur-de-lys on each end in navy blue. I also marked off a horizontal stripe with Frog tape and painted that navy as well.
Once Ellie realized the crib was for her and not for Ada on Christmas morning, she squealed and ran right over to it. There was some initial confusion over who was meant to go in the "cribby," though...
Good to know it's sturdy enough to hold a 25 lb. two year old!
Since returning home Ellie's dolls have been on rotation through the crib and she really seems to love it. Which makes me feel good, obviously :)