- Set up an 8x11" page in InDesign
- Actually, configure 2 pages, both with the same Master Page applied.
- Set the 2 pages as a "spread", not "facing pages", just a side by side spread. ("Allow Document Pages to shuffle" for the Pages Panel Options, and drag the pages together.)
- Design as desired on the master page:

Note the master page, being applied to the 2 spread pages means there's 1 design on 2 pages. You simply always edit the master page.

When printing
(The print Preview below will not show the correct print page size because my printer driver doesn't support 11x17" [tabloid]. However, these settings will work, and your preview page size should show you the desired preview.)
- Tick the Spreads option in the
General
settings:

- Set the Page Size and then change the Page Position dropdown menu to Upper Left in the
Setup
settings:

This should all result in a 2-up sheet, on the left side of the 11x17" stock, leaving 1" on the right side to be trimmed.
If you are printing both sides of the 11x17" (4 total impressions) -- for the reverse side, it's a matter of feeding the already printed pieces into the printer correctly so that both sides are butted against the same edge. This may or may not mean you need to print one side upside down, which may mean you need to actually rotate your design 180° on the page first (kind of depends upon the printer). Also note: running printed sheets through an end-use printer can cause damage to the printer if it's not designed for duplex printing. If it is designed for duplex printing, you may be able to merely print 2 copies, duplex, and get the desired results.
InDesign CS6 screen shots... but it should be pretty much the same in newer versions.
based on comments under the question...
If you already have both pages in a spread.. just use the print settings above. You can ignore the Master Page stuff. However, configuring the file that way will make editing easier overall.