Follow the diagrams below to assemble the base.

Here are parts to assemble one end. Make sure you have the two frame long sides and one end placed with their bottom side up.

You should work on a flat bench or protected table surface that has clear space about twice as long as the length of the base you bought.
Now two of the small elbows with screws should have their screws slackened off and placed on top of two of the plain elbows, to make a two layer sandwich with the screws on top.

Slide the sandwiched elbows into both ends of the short frame piece as shown above. They should go in easily. The screws are not backed off enough if they are too tight.

Now slide one long frame side into one elbow sandwich and with those frame corner pieces fully pressed together, lightly tight the elbow screws there until the joint is firm.

Now slide the other long frame side into the other elbow sandwich and with those frame second corner pieces fully pressed together, lightly tight the elbow screws on the second corner until the second joint is firm.

Now turn the "U" shape frame the right way up. Gently slide the foam core support board piece about half-way into the "U" end, using the wide frame slots.

(Note: if you have the 38" long base version - feed the second foam core board in behind the first, then extra carefully, preferably with thick gloves on, because the edges are thin and sharp and under tension, unroll the two springy rolled up steel sheets where they can lay out flat.)

Next, without kinking it, carefully slide the thicker magnetic steel sheet on top of the foamcore board about as far as shown and finally add the top surface stainless steel thinner sheet on top of that, as far in to match the picture.

Now slowly slide the foamcore base, then the middle steel surface and finall the top stainless steel surface all the way into the "U" end and under the end frame slot edge.

Turn the loaded "U" frame back upside down. Next repeat the process of adding the elbow sandwiches to the other short frame section, then slide it onto the open end of the assembled "U" frame, making sure the surfaces slide safely under the edge of the top slot before pushing it fully home.
Lightly tighten the elbow screws to fix the second frame end firmly closed.

Finally, compress the surface holding springs and slide them under the frame edges as shown. One at each end and the rest evenly spaced along the long sides.

The base is now completely assembled.