FirstPage_LeftHand.jsx

//refer to  https://indesignsecrets.com/starting-a-document-on-a-left-hand-page.php
if(app.documents.length !== 0){
	app.doScript(function() {
		try {
			var d = app.activeDocument;
			p1 = d.pages[0];
			p1.appliedSection.continueNumbering = false;
			p1.appliedSection.pageNumberStart = 2;
			d.spreads.everyItem().allowPageShuffle = false;
			p1.appliedSection.pageNumberStart = 1;
		} catch (e) {}
	}, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, "FirstPage_LeftHand");
}