Building a riser. First time diy.

[Infrared Sight]

I uploaded a couple pics of where I want the riser to be. I have planned to build it using 2x12 wood. For the step I will use a 2x6, or just cut the 2x12 where I need to. I am planning to get new seats for the front next year, thus the project, so people can see the tv from the couch. Those front seats have seen better days. Too much jumping on them. lol.
The whole riser will come up to the 3 wall sides, so I can move the couch on one side for holiday time. The approx area will be 139"x64" I will be adding carpet to it as well as close as I can get to my current color. Haven't decided to do it myself or not. Need to research prices on that.
For the insulation I have seen some people put pillows in there. Would that be better then normal insulation? Opinions needed. Thanks.


My costs for the riser.
R30 Insulation:2@6.56 each
Safety Kit for Insulation:1@6.87
2x8x8 Wood:6@4.68 each
2x12x12 Wood:3@12.35 each
2X12X8 Wood:1@8.23
19/32x4x8 Plywood:3 OSB Rated@9.97 each
Screws:1 box 2" Gold Screw@5.94
Carpet:12'x9'@85.56
Padding:6x9 2@32.67
Installation:75.00

Total=Around $355