Materials, cost, and build time will all vary depending on the design and method you choose for assembling the Dice Tray. The following is summary of my approach, but your experience may be different.
WOOD BOX (140 x 140 x 65 mm)
DISPOSABLE CHOPSTICKS (14 pairs + extra in case of splitting)
AIR-DRY CLAY (about a baseball's worth)
THIN DOORMAT (synthetic felt; without rubber backing)
WATER-BASED PAINT (liquid in tubes)
VARNISH (brush-on; designed for clay, wood, and paper)
HOT GLUE GUN
"X-ACTO" KNIFE / CUTTING PAD / STEEL RULER
LARGE PAPERCLIP / TOOTHPICK / ETC. (for shaping clay)
* I get materials for almost all of my projects at the dollar store.
** Below costs are for the materials and how much I used (of things that can be used for other projects as well).
BOX: Total=$1.00 This Project=$1.00
DOORMAT: Total=$1.00 This Project=$0.50
CLAY: Total=$1.00 This Project=$0.30
PAINT: Total=$1.00 This Project=$0.10
VARNISH: Total=$3.00 This Project=$0.80
CHOPSTICKS: FREE (I always ask for extra when I order-out)
Expendature for this project: $2.70
Step 1 - 00:45 (work)
Step 2 - 00:30 (work) 24:00 (dry time)
Step 3 - 00:15 (work) 24:00 (dry time)
Step 4 - 00:30 (work) 24:00 (dry time)
Step 5 - 00:30 (work)
Time for this project: 2.5 Hours working + 3 Days allowing to dry
As the pictures show, I decided to finish the sides with a stone wall topped by Tudor style framed walls. If you choose solid stone walls, chopsticks may not be necessary; or for Tudor walls with no stone, shredded toilet paper mixed with glue (or just wrinkled paper) could be used in place of clay. Small round gravel pressed into clay could produce a "cobblestone" effect, or lining the sides with unbroken rows of chopsticks could end up looking like wood paneling.
Again, there are a lot of options, so decide what "look" you're going for before you purchase materials!