Attach all the pieces together. Then, make the railing. Use 1x4’s for the top and bottom of the railings with 1x2’s cut at 11 ½” long for the up and down part of the railings. Space evenly with 3” between slats. Note: Especially on the back, please cut length to exact measurement, as yours may differ slightly!
Stairs outer edge: Cut 1x4’s to 15 7/8”, use 4 slats
Stairs inner edge: 1x4’s to 25”, use 6 slats
Front center: 1x4’s to 47”, use 10 slats
Front right: 1x4 to 2 ¼”, use 1 slat
Slide inner side: 1 x 4 to 25 ½”, use 6 slats
Slide outer side: 1 x 4 to 13 1/16”, use 3 slats
Back: 1 x 4 to 115 ¾”, use 26 slats
I used 1x3 instead of 1x2 at some of the intersections of pieces, just a preference.
Attach all the slats to the bed. Since the railing against the wall supports the mattress, I then used bolts to attach the top railing to studs in the wall. I did this about four times across the bed and it really helped with the support and to keep the railing from being pulled away from the wall.
Also, for the slide inner edge and the stairs inner edge, there wasn't as much support as I wanted. So, I bought a couple of L brackets (used to put up shelvings and such) and attached one to each set of railings, with the other end of the L bracket being attached to the under bed slats.