What you need:
4 quartz blocks
2 quartz slab
1 nether reactor core
1 painting
1 trap door
First, have an area that is 2×2 in a corner.
Next, surround the 2×2 space with the 4 quartz blocks(3 blocks going left and 1 back)
Next, place 1 of the quartz slabs on the last quartz block then place the trap door onto the slab.
Last, place the nether reactor core onto the 1st(first) quartz block,put a painting on tthe nether reactor core and place the 2nd(second) quartz slab on the quartz block.