yes get the smaller size


https://www.homedepot.com/p/UltraTouch-48-in-x-6-ft-Radiant-Barrier-30000-11406/100656748

and this fire blanket

https://www.amazon.com/Emergency-survival-Fiberglass-Blanket-fireplace/dp/B071744PRN/ref=sr_1_1_sspa?

use a piece of plywood


https://www.homedepot.com/p/Underlayment-Common-7-32-in-x-4-ft-x-8-ft-Actual-0-196-in-x-48-in-x-96-in-431178/203183010

make it  1 ft by 6 ft     four pieces

you have a left over  piece 2 ft by 4 foot.

the 4 long pieces make a U shape  line with the liner  you will have a left over piece of liner  use that for the top board.

the box will be 1 ft by 1 ft by 6 foot  the inside will be  11 inches by 11 inches it will fit the miner and the psu.