You can inherit the products_item template to base price in shop page for all product items:

<template id="products_base_price" inherit_id="website_sale.products_item">
    <xpath expr="//*[hasclass('product_price')]" position="after">
        <div class="product_price mb-1" itemprop="offers" itemscope="itemscope" itemtype="http://schema.org/Offer">
            <span>Base price:</span>
            <span itemprop="base_price" style="" t-esc="product.standard_price"
                  t-options="{'widget': 'monetary', 'display_currency': website.currency_id}"/>
        </div>
    </xpath>
</template>

And you inherit the product_price to add base price in product page as below:

<template id="product_price" inherit_id="website_sale.product_price">
    <xpath expr="//h4[hasclass('css_non_editable_mode_hidden','decimal_precision')]" position="after">
        <div itemprop="offers" itemscope="itemscope" itemtype="http://schema.org/Offer" class="product_price mb-1">
            <h4 class="css_editable_mode_hidden">
                <span>Base price:</span>
                <span itemprop="base_price" style="" t-esc="product.standard_price"
                      t-options="{'widget': 'monetary', 'display_currency': website.currency_id}"/>
            </h4>
        </div>
    </xpath>
</template>