Obtain your supplies.
I got most of my metal parts from a metal shop as scraps and only paid a few bucks for them (the Square steel plate, cylinderical rod welded to it and the two long rectangle pieces)
I am convinced that if you do not have access to a metal shop or store you can use 2x4’s for the two long rectangle pieces.
As for the Welded plate and Cylinderical rod, if you don’t know anyone who can weld you can a pre-fabricated “Flange” at home depot.
You will want about 8ft of steel cable (thin) will be 4ft for each side.
You will also need the conectors for the cable, dont know what they are called but they are the to small metal pieces with the 2 holes and the two metal tear drop looking pieces.
You will need 2 U-bolts, these actually screw together.
Enough 1/4inch rubber material or carpet to make 2 squares big enough that a 45lb plate can lay on it with some overlap.
Nuts and bults to hold the Flange to the rubber mat and the two long metal pieces plus the two rubber mats between them together.