Create custom search form indexed_search TYPO3 v8

I'm trying to add a custom search form into my template, the TypoScript I used in a v7 install no longer works.

If I copy the Fluid form used in the extension (Form.html) and place it into one of my Fluid template a search box appears but it posts back to itself, even though I have set a rootPidList in my constants. This is the code I copy:

<f:form action="search" method="post" id="tx_indexedsearch" pageUid="{settings.targetPid}">
<div class="tx-indexedsearch-hidden-fields">
    <f:form.hidden name="search[_sections]" value="0" />
    <f:form.hidden name="search[_freeIndexUid]" id="tx_indexedsearch_freeIndexUid" value="_" />
    <f:form.hidden name="search[pointer]" id="tx_indexedsearch_pointer" value="0" />
    <f:form.hidden name="search[ext]" value="{searchParams.ext}" />
    <f:form.hidden name="search[searchType]" value="{searchParams.searchType}" />
    <f:form.hidden name="search[defaultOperand]" value="{searchParams.defaultOperand}" />
    <f:form.hidden name="search[mediaType]" value="{searchParams.mediaType}" />
    <f:form.hidden name="search[sortOrder]" value="{searchParams.sortOrder}" />
    <f:form.hidden name="search[group]" value="{searchParams.group}" />
    <f:form.hidden name="search[languageUid]" value="{searchParams.languageUid}" />
    <f:form.hidden name="search[desc]" value="{searchParams.desc}" />
    <f:form.hidden name="search[numberOfResults]" value="{searchParams.numberOfResults}" />
    <f:form.hidden name="search[extendedSearch]" value="{searchParams.extendedSearch}" />
</div>
<fieldset>
    <legend><f:translate key="form.legend" /></legend>
    <div class="tx-indexedsearch-form">
        <label for="tx-indexedsearch-searchbox-sword"><f:translate key="form.searchFor" />:</label>
        <f:form.textfield name="search[sword]" value="{sword}" id="tx-indexedsearch-searchbox-sword" class="tx-indexedsearch-searchbox-sword" />
    </div>
    <div class="tx-indexedsearch-search-submit">
        <f:form.submit name="search[submitButton]" value="{f:translate(key: 'form.submit')}" id="tx-indexedsearch-searchbox-button-submit" class="tx-indexedsearch-searchbox-button" />
    </div>
</fieldset>

And my typoscript:

config.index_enable = 1
page.config.index_enable = 1
plugin.tx_indexedsearch.settings.targetPid = 31

If I add the stock indexed search plugin to a random page, this will work. Just to rule it out, I've also disable realurl just in case.

Thanks again T3 community.

Solution

if you just copy the search template into your output/ page template, there is no plugin available which provides values for the specific variables needed in this template-part.

either you use an output of a page where you have inserted the plugin (copy from HTML-source)
or you insert the plugin in all pages:
- this can be done with a column you inherit and where the plugin is inserted on top level
- or you use typoscript to render the plugin into a fluid-variable and display the generated HTML in your (page-)template.